B) Performing the trace within the Cisco FMC GUI instead of the Cisco FMC CLI is not a valid option, because the FMC GUI does not support packet capture or tracing on the FTD device. You can only use the FMC GUI to view and export captures that are taken on the FTD CLI1.
C) Using the verbose option as a part of the capture-traffic command is not a valid option, because there is no verbose option for this command. The verbose option is only available for the capture command, which is used to capture packets on the LINA engine domain of the FTD device1.
D) Using the capture command and specifying the trace option to get the required information is not a valid option, because the capture command does not have a trace option. The capture command allows you to capture packets on the LINA engine domain of the FTD device, but it does not show the Snort detection actions. The trace option is only available for the packet-tracer command, which is used to simulate a packet going through the FTD device and show its processing steps1.
Explanation:
The correct answer is A.
Specify the trace using the -T option after the capture-traffic command. According to the document Use Firepower Threat Defense Captures and Packet Tracer, the capture-traffic command allows you to capture packets on the Snort engine domain of the FTD device. However, by default, it only shows the packet headers and does not include the Snort detection actions. To see the Snort detection actions, you need to use the -T option, which enables tracing. For example:
capture-traffic -T
This will show the packet headers along with the Snort verdicts, such as allow, block, or replace. You can also use other options to filter or save the capture output1.