one advantage of communicating via e-mail is that it is
a)temporary and can be deleted
b)a permanent record
c)a secure and private communication
d)informal

One advantage of communicating via e-mail is that it is C) a secure and private communication.

Explanation:

Now a days communicating via e-mail is a secure and private way to communicate. It is often necessary for work, everyone now a days is using this tool to send messages to one and other and now that it would be private and also effective. It is secure because you now it won´t get lost or missplaced, it is certain tan the e mail you sent would be most likely delivered, and also you can be certain that no one but the owner of the e mail adress would read it.

It is no only used for working reasons, it can also be a way to contact someone for personal reasons, to confirm appointments, to even send medical results. Now a days even laboratory results are sent by mail, that is how private and secure communicating via e mail is.

2nd option

explanation:

the answer should be the first one. "many people find his lyrics very moving."

it by far makes the most grammatical sense and is very objective, removing any first person from the original sentence and keeping with the sentence fluency.