What are the main drawbacks for anti-virus software?

What are the main drawbacks for anti-virus software?

A.
AV software is difficult to keep up to the current revisions.

B.
AV software can detect viruses but can take no action.

C.
AV software is signature driven so new exploits are not detected.

D.
It’s relatively easy for an attacker to change the anatomy of an attack to bypass AV systems

E.
AV software isn’t available on all major operating systems platforms.

F.
AV software is very machine (hardware) dependent.

Explanation:
Although there are functions like heuristic scanning and sandbox technology,the
Antivirus program is still mainly depending of signature databases and can only find already
known viruses.