Answer: Cory is demonstrating: b) selective attention.
Explanation:
Selective attention occurs when we filter everything out which seem irrelevant to us at that moment and focus solely on that one aspect of which we are interested in at that particular moment. Instead of listening or paying attention to various objects we choose one that interests us and tune out all those that don't matter to us.
Corey is able to not look at the newsfeed and advertisements because he is solely focused on reading what his friend wrote hence he tunes out all the aspects he isn't interested in.