The transaction command is a Splunk command that finds transactions based on events that meet various constraints1.
Transactions are made up of the raw text (the _raw field) of each member, the time and date fields of the earliest member, as well as the union of all other fields of each member1.
The transaction command adds some fields to the raw events that are part of the transaction12. These fields are:
duration: The difference, in seconds, between the timestamps for the first and last events in the transaction12.
eventcount: The number of events in the transaction12.
closed_txn: A Boolean field that indicates whether the transaction is closed or evicted2. A transaction is closed if it meets one of the following conditions: maxevents, maxpause, maxspan, or startswith2. A transaction is evicted if it does not meet any of these conditions and exceeds the memory limit specified by maxopentxn or maxopenevents23.
Therefore, evicted transactions can be distinguished from non-evicted transactions by checking the value of the closed_txn field. The closed_txn field is set to 0, or false, for evicted transactions and 1, or true for non-evicted, or closed, transactions23.

The transaction command is a search command that creates a single event from a group of events that share some common characteristics. The transaction command can group events based on fields, time, or both. The transaction command can also create some additional fields for each transaction, such as duration, eventcount, startime, etc. The transaction command does not group a set of transactions based on time, but rather groups a set of events into a transaction based on time. The transaction command does not separate two events based on one or more values, but rather joins multiple events based on one or more values. The transaction command does not return the number of credit card transactions found in the event logs, but rather creates transactions from the events that match the search criteria.

Reference:
A macro is a reusable search string that can contain any part of a search, such as search terms, commands, arguments, etc. A macro can have a flexible time range that can be specified when the macro is executed. A macro can also have arguments that can be passed to the macro when it is executed. A macro can be created by using the Settings menu or by editing the macros.conf file. A macro does not have to contain the full search, but only the part that needs to be reused. A macro does not have to have a fixed time range, but can use a relative or absolute time range modifier. A macro does not have to contain only a portion of the search, but can contain multiple parts of the search.

Explanation
The correct answer is D. An argument can be passed to the inner macro by nesting parentheses.
A search macro is a way to reuse a piece of SPL code in different searches. A search macro can take arguments, which are variables that can be replaced by different values when the macro is called. A search macro can also contain another search macro within it, which is called a nested macro. A nested macro can also take arguments, which can be passed from the outer macro or directly from the search string.
To pass an argument to the inner macro, you need to use parentheses to enclose the argument value and separate it from the outer macro argument. For example, if you have a search macro named outer_macro (1) that contains another search macro named inner_macro (2), and both macros take one argument each, you can pass an argument to the inner macro by using the following syntax:
outer_macro (argument1, inner_macro (argument2))
This will replace the argument1 and argument2 with the values you provide in the search string. For example, if you want to pass "foo" as the argument1 and "bar" as the argument2, you can write:
outer_macro ("foo", inner_macro ("bar"))
This will expand the macros with the corresponding arguments and run the SPL code contained in them.
References:
Search macro examples
Use search macros in searches