What is an important factor affecting the time required to perpetrate a manual trial and error attack
to gain access to a target computer system?

A.
Keyspace for the password.

B.
Expertise of the person performing the attack.

C.
Processing speed of the system executing the attack.

D.
Encryption algorithm used for password transfer.

Explanation:
I am not sure of the answer on this question. B seems good but the reference below states that
Keyspace (or length of password) is the main deterrent. I did not come across something that
directly relates in my readings. “If an attacker mounts a trial-and-error attack against your password,
a longer password gives the attacker a larger number of alternatives to try. If each character in the
password may take on 96 different values (typical of printable ASCII characters) then each additional
character presents the attacker with 96 times as many passwords to try. If the number of
alternatives is large enough, the trial-and-error attack might discourage the attacker, or lead to the
attacker’s detection.” http://www.smat.us/sanity/riskyrules.html