The statement that can be used to change the contents of a row of data in an internal table is MODIFY table. The MODIFY table statement can be used to change the contents of one or more rows of an internal table, either by specifying the table index, the table key, or a condition. The MODIFY table statement can also be used to change the contents of a database table, by specifying the table name and a work area or an internal table. The MODIFY table statement can use the TRANSPORTING addition to specify which fields should be changed, and the WHERE addition to specify which rows should be changed.
The other statements are not suitable for changing the contents of a row of data in an internal table, as they have different purposes and effects. These statements are:
APPEND table: This statement can be used to add a new row of data to the end of an internal table, either by specifying a work area or an inline declaration. The APPEND table statement does not change the existing rows of the internal table, but only increases the number of rows by one.
INSERT table: This statement can be used to insert a new row of data into an internal table, either by specifying the table index, the table key, or a sorted position. The INSERT table statement does not change the existing rows of the internal table, but only shifts them to make room for the new row. The INSERT table statement can also be used to insert a new row of data into a database table, by specifying the table name and a work area or an inline declaration.
UPDATE table: This statement can be used to update the contents of a database table, by specifying the table name and a work area or an internal table. The UPDATE table statement can use the SET addition to specify which fields should be updated, and the WHERE addition to specify which rows should be updated. The UPDATE table statement does not affect the internal table, but only the corresponding database table.

A field symbol is a pointer that allows direct access to a row of an internal table without copying it to a work area. Using a field symbol for internal table row access has some advantages over using a work area, such as12:
* A MODIFY statement to write changed contents back to the table is not required: This is true. When you use a work area, you have to copy the row content from the internal table to the work area, modify it, and then copy it back to the internal table using the MODIFY statement. This can be costly in terms of performance and memory consumption. When you use a field symbol, you can modify the row content directly in the internal table without any copying. Therefore, you do not need the MODIFY statement12.
* Using a field symbol is faster than using a work area: This is true. As explained above, using a field
* symbol avoids the overhead of copying data between the internal table and the work area. This can improve the performance of the loop considerably, especially for large internal tables. According to some benchmarks, using a field symbol can save 25-40% of the runtime compared to using a work area12.
You cannot do any of the following:
* The field symbol can be reused for other programs: This is false. A field symbol is a local variable that is only visible within the scope of its declaration. It cannot be reused for other programs unless it is declared globally or passed as a parameter. Moreover, a field symbol must have the same type as the line type of the internal table that it accesses. Therefore, it cannot be used for any internal table with a different line type12.
* The row content is copied to the field symbol instead to a work area: This is false. As explained above, using a field symbol does not copy the row content to the field symbol. Instead, the field symbol points to the memory address of the row in the internal table and allows direct access to it. Therefore, there is no copying involved when using a field symbol12.
References: 1: Using Field Symbols to Process Internal Tables - SAP Learning 2: Access to Internal Tables - ABAP Keyword Documentation - SAP Online Help

The statement that can be used to expose the field "connid" of the data source "demo_ods_assoc_spfli" in the element list is A. demo_ods_assoc_spfli.connid,. This statement uses the dot notation to access the field
"connid" of the data source "demo_ods_assoc_spfli", which is an association defined on line #4. The association "demo_ods_assoc_spfli" links the data source "demo_ods" with the table "spfli" using the field
"carrid". The statement also ends with a comma to separate it from the next element in the list12.
You cannot do any of the following:
* B. demo_ods_assoc_spfli-connid/: This statement uses the wrong syntax to access the field "connid" of the data source "demo_ods_assoc_spfli". The dash notation is used to access the components of a structure or a table, not the fields of a data source. The statement also ends with a slash, which is not a valid separator for the element list12.
* C. spfli-connid,: This statement uses the wrong data source name to access the field "connid". The data source name should be "demo_ods_assoc_spfli", not "spfli". The statement also uses the wrong syntax to access the field "connid", as explained above12.
* D. _spfli.connid/: This statement uses the wrong data source name and the wrong separator to access the field "connid". The data source name should be "demo_ods_assoc_spfli", not "_spfli". The statement also ends with a slash, which is not a valid separator for the element list12.
References: 1: ABAP CDS - SELECT, select_list - ABAP Keyword Documentation - SAP Online Help 2: ABAP CDS - SELECT, from - ABAP Keyword Documentation - SAP Online Help

The function find_any_not_of returns the position of the first character in the string val that is not contained in the string sub. If no such character is found, the function returns 0. In this case, the string val contains only the characters A, B, and a, which are all contained in the string sub, so the function returns 0. The other functions return positive values, as follows:
* Count_any_of returns the number of occurrences of any character in the string sub within the string val.
In this case, it returns 8, since there are 8 A's and B's in val.
* Count returns the number of occurrences of the string sub within the string val. In this case, it returns 2, since there are 2 AB's in val.
* find_any_of returns the position of the first character in the string val that is contained in the string sub.
In this case, it returns 1, since the first character A is in sub. References: String Functions - ABAP Keyword Documentation, Examples of String Functions - ABAP Keyword Documentation

When accessing the subclass instance through go_super, you can do both of the following:
* Access the inherited private components: A subclass inherits all the private attributes and methods of its superclass, unless they are explicitly overridden by the subclass. Therefore, you can access the inherited private components of the superclass through go_super, as long as they are not hidden by other attributes or methods in the subclass12.
* Access the inherited public components: A subclass inherits all the public attributes and methods of its superclass, unless they are explicitly overridden by the subclass. Therefore, you can access the inherited public components of the superclass through go_super, as long as they are not hidden by other attributes or methods in the subclass12.
You cannot do any of the following:
* Call a subclass specific public method: A subclass does not have any public methods that are not inherited from its superclass. Therefore, you cannot call a subclass specific public method through go_super12.
* Call inherited public redefined methods: A subclass does not have any public methods that are redefined from its superclass. Therefore, you cannot call inherited public redefined methods through go_super12.
References: 1: Object Oriented - ABAP Development - Support Wiki 2: Inheritance and Instantiation - ABAP Keyword Documentation