Which of the following commands could be used to verify that the company is able to connect to the mail service at CompTIA.org?

Several users are sending emails to CompTIA.org. but they are not being received. Which of
the following commands could be used to verify that the company is able to connect to the
mail service at CompTIA.org?

A.
Ping

B.
Arp

C.
Dig

D.
telnet