Answer:
focusing on personal appearance
Explanation:
Marshall has the preconceived notion that young people are the only ones who are knowledgeable about new technology. He could not accept the fact that a middle aged woman would be knowledgeable about new technology.
It also could have been that she merely looks older than she appears
His lack of acceptance of the fact was significant enough to distract him from what he was trying to say.
Hence, Marshall was focusing on personal appearance.