You could always answer;

"I'd hand the PA mic to the Capt. and say, 'Here, you do it'. Because it's his airplane, if he wants to lie to the passengers, that's his decision, but I'm not going to do it for him."

OR...you could just say, "Yes Sir" and be done with it.

Perhaps they are not looking for a 'right' answer, but rather your attitude in answering the question.

Now, in the real world, as a newbie on probation, I'd probably say "Yes Sir."

But as a 15yr. F/O, I'd probably tell him to do it himself.