Answer:
The tool that can help detect trojans by displaying ports on which the computer is listening is (a) netstat.
Step-by-step explanation:
Netstat (Network Statistics) is a command-line tool available in most operating systems, including Windows, Linux, and macOS. It provides information about network connections, network interfaces, and listening ports on a computer. By using the appropriate parameters, netstat can display a list of active network connections, including the local and remote IP addresses and the associated ports.
To detect trojans, you can use netstat to identify any suspicious or unknown connections or listening ports on your computer. Unusual or unauthorized connections or open ports may indicate the presence of a trojan or other malicious software. By examining the netstat output and investigating any suspicious connections, you can identify potential security threats and take appropriate actions to mitigate them.