Explanation
A macro is a way to save a commonly used search string as a variable that you can reuse in other searches1. When you create a macro, you can define arguments that are placeholders for values that you specify at execution time1. The argument values are used to resolve the search string when the macro is invoked, not when it is created1. Therefore, statements B and C are true, while statements A and D are false.

The correct syntax to find events associated with a tag in Splunk is tag=<value>1. So, the correct answer is D) tag=<value>. This syntax allows you to annotate specified fields in your search results with tags1.
In Splunk, tags are a type of knowledge object that you can use to add meaningful aliases to field values in your data1. For example, if you have a field called status_code in your data, you might have different status codes like 200, 404, 500, etc. You can create tags for these status codes like success for 200, not_found for 404, and server_error for 500. Then, you can use the tag command in your searches to find events associated with these tags1.
Here is an example of how you can use the tag command in a search:
index=main sourcetype=access_combined | tag status_code
In this search, the tag command annotates the status_code field in the search results with the corresponding tags. If you have tagged the status code 200 with success, the status code 404 with not_found, and the status code 500 with server_error, the search results will include these tags1.
You can also use the tag command with a specific tag value to find events associated with that tag. For example, the following search finds all events where the status code is tagged with success:
index=main sourcetype=access_combined | tag status_code | search tag::status_code=success In this search, the tag command annotates the status_code field with the corresponding tags, and the search command filters the results to include only events where the status_code field is tagged with success1.

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]

https://docs.splunk.com/Documentation/Splunk/8.0.2/Knowledge/CreateworkflowactionsinSplunkWeb