What are the limitations of Vulnerability scanners?

What are the limitations of Vulnerability scanners? (Select 2 answers)

A.
There are often better at detecting well-known vulnerabilities than more esoteric ones

B.
The scanning speed of their scanners are extremely high

C.
It is impossible for any,one scanning product to incorporate all known vulnerabilities in a timely
manner

D.
The more vulnerabilities detected,the more tests required

E.
They are highly expensive and require per host scan license