D , had something like this in a mock. Phishing is about tricking users more than bypassing tech controls, so user awareness training (D) gets to the root cause. Firewalls and patches won’t really stop someone from clicking a suspicious link. Pretty sure D is the intended answer here, but if anyone thinks otherwise, I’m interested to hear it.
Don't think A really addresses phishing directly. D is the better fit since awareness training actually deals with people getting tricked, not just software flaws. Pretty sure that's what they want here, though A often catches folks out.