A delimiter field extraction is a method of extracting fields from data that uses a character or a string to separate fields in each event. A delimiter field extraction can be performed by using the Field Extractor (FX) tool or by editing the props.conf file. A delimiter field extraction can be applied to any file format that uses a delimiter to separate fields, such as CSV, TSV, PSV, etc. A CSV file is a comma-separated values file that uses commas as delimiters. Therefore, a CSV file can be extracted using a delimiter field extraction.

Explanation
A comparison operator is a symbol that compares two values and returns a Boolean result (true or false)2. Splunk supports various comparison operators such as <, >, =, !=, <=, >=, IN and LIKE2. However,
?= is not a valid comparison operator in Splunk and will cause a syntax error if used in a search string2.
Therefore, option E is correct, while options A, B, C and D are incorrect because they are valid comparison operators in Splunk

Reference: https://docs.splunk.com/Documentation/Splunk/8.0.3/SearchReference/Transaction One of the statements that would help a user choose between the transaction and stats commands is that there is a 1000 event limitation with the transaction command3. The transaction command is used to group events that share a common value for one or more fields into transactions3. The transaction command has a default limit of 1000 events per transaction, which means that it will not group more than 1000 events into a single transaction3. This limit can be changed by using the maxevents parameter, but it can affect the performance and memory usage of Splunk3. Therefore, option C is correct, while options A, B and D are incorrect because they are not statements that would help a user choose between the transaction and stats commands.

Explanation
The correct answer is A. chart, timechart, stats, eventstats.
Transforming commands are commands that change the format of the search results into a table or a chart.
They can be used to perform statistical calculations, create visualizations, or manipulate data in various ways1.
Transactions are groups of events that share some common values and are related in some way. Transactions can be defined by using the transaction command or by creating a transaction type in the transactiontypes.conf file2.
Some transforming commands can be used with transactions to create tables or charts based on the transaction fields. These commands include:
chart: This command creates a table or a chart that shows the relationship between two or more fields. It can be used to aggregate values, count occurrences, or calculate statistics3.
timechart: This command creates a table or a chart that shows how a field changes over time. It can be used to plot trends, patterns, or outliers4.
stats: This command calculates summary statistics on the fields in the search results, such as count, sum, average, etc. It can be used to group and aggregate data by one or more fields5.
eventstats: This command calculates summary statistics on the fields in the search results, similar to stats, but it also adds the results to each event as new fields. It can be used to compare events with the overall statistics.
These commands can be applied to transactions by using the transaction fields as arguments. For example, if you have a transaction type named "login" that groups events based on the user field and has fields such as duration and eventcount, you can use the following commands with transactions:
| chart count by user : This command creates a table or a chart that shows how many transactions each user has.
| timechart span=1h avg(duration) by user : This command creates a table or a chart that shows the average duration of transactions for each user per hour.
| stats sum(eventcount) as total_events by user : This command creates a table that shows the total number of events for each user across all transactions.
| eventstats avg(duration) as avg_duration : This command adds a new field named avg_duration to each transaction that shows the average duration of all transactions.
The other options are not valid because they include commands that are not transforming commands or cannot be used with transactions. These commands are:
diff: This command compares two search results and shows the differences between them. It is not a transforming command and it does not work with transactions.
datamodel: This command retrieves data from a data model, which is a way to organize and categorize data in Splunk. It is not a transforming command and it does not work with transactions.
pivot: This command creates a pivot report, which is a way to analyze data from a data model using a graphical interface. It is not a transforming command and it does not work with transactions.
References:
About transforming commands
About transactions
chart command overview
timechart command overview
stats command overview
[eventstats command overview]
[diff command overview]
[datamodel command overview]
[pivot command overview]