Explanation
Correct code block:
itemsDf.withColumn("itemNameElements", split("itemName"," "))
Output of code block:
+------+----------------------------------+-------------------+------------------------------------------+
|itemId|itemName |supplier |itemNameElements |
+------+----------------------------------+-------------------+------------------------------------------+
|1 |Thick Coat for Walking in the Snow|Sports Company Inc.|[Thick, Coat, for, Walking, in, the, Snow]|
|2 |Elegant Outdoors Summer Dress |YetiX |[Elegant, Outdoors, Summer, Dress] |
|3 |Outdoors Backpack |Sports Company Inc.|[Outdoors, Backpack] |
+------+----------------------------------+-------------------+------------------------------------------+ The key to solving this question is that the split method definitely needs a second argument here (also look at the link to the documentation below). Given the values in column itemName in DataFrame itemsDf, this should be a space character " ". This is the character we need to split the words in the column.
More info: pyspark.sql.functions.split - PySpark 3.1.1 documentation
Static notebook | Dynamic notebook: See test 1

Explanation
Correct code block:
transactionsDf.repartition(1).write.option("sep", "\t").option("nullValue", "n/a").csv(csvPath) It is important here to understand that the question specifically asks for writing the DataFrame as a single CSV file. This should trigger you to think about partitions. By default, every partition is written as a separate file, so you need to include repatition(1) into your call. coalesce(1) works here, too!
Secondly, the question is very much an invitation to search through the parameters in the Spark documentation that work with DataFrameWriter.csv (link below). You will also need to know that you need an option() statement to apply these parameters.
The final concern is about the general call structure. Once you have called accessed write of your DataFrame, options follow and then you write the DataFrame with csv. Instead of csv(csvPath), you could also use save(csvPath, format='csv') here.
More info: pyspark.sql.DataFrameWriter.csv - PySpark 3.1.1 documentation Static notebook | Dynamic notebook: See test 1

Explanation
Dynamic partition pruning reoptimizes query plans based on runtime statistics collected during query execution.
No - this is what adaptive query execution does, but not dynamic partition pruning.
Dynamic partition pruning concatenates columns of similar data types to optimize join performance.
Wrong, this answer does not make sense, especially related to dynamic partition pruning.
Dynamic partition pruning reoptimizes physical plans based on data types and broadcast variables.
It is true that dynamic partition pruning works in joins using broadcast variables. This actually happens in both the logical optimization and the physical planning stage. However, data types do not play a role for the reoptimization.
Dynamic partition pruning performs wide transformations on disk instead of in memory.
This answer does not make sense. Dynamic partition pruning is meant to accelerate Spark - performing any transformation involving disk instead of memory resources would decelerate Spark and certainly achieve the opposite effect of what dynamic partition pruning is intended for.

Explanation
In this question it is important to realize that you are asked to sort transactionDf by two columns. This means that the sorting of the second column depends on the sorting of the first column.
So, any option that sorts the entire DataFrame (through chaining sort statements) will not work. The two columns need to be channeled through the same call to sort().
Also, order_by is not a valid DataFrame API method.
More info: pyspark.sql.DataFrame.sort - PySpark 3.1.2 documentation
Static notebook | Dynamic notebook: See test 2

Explanation
This question targets your knowledge about how to chain filtering conditions. Each filtering condition should be in parentheses. The correct operator for "or" is the pipe character (|) and not the word or. Another operator of concern is the equality operator. For the purpose of comparison, equality is expressed as two equal signs (==).
Static notebook | Dynamic notebook: See test 2