Answer:
Option D i.e., Mail User Agent is the correct option.
Explanation:
The Mutt software is software that works as the mail client on Linux or Unix Operating Systems and MUA(Mail User Agent) is also the mail client that provides its users the facility of sending and receiving emails through the internet and it does not provide the offline access. So the Mutt software is the type of Mail User Agent which is based on the mail client.
