A penetration tester has been given eight business hours to gain access to a client's financial system.
Which of the following techniques will have the HIGHEST likelihood of success?

A. Attempting to tailgate an employee who is going into the client's workplace
B. Dropping a malicious USB key with the company's logo in the parking lot
C. Using a brute-force attack against the external perimeter to gain a foothold
D. Performing spear phishing against employees by posing as senior management