Answer:
I believe it is the second one (Unless everyone in the U. S. Including our grandparents can successfully use social media, we will be left behind.)
Explanation:
A fallacy is when an argument is made that is not sound. 'Unless everyone in the U. S. Including our grandparents can successfully use social media, we will be left behind.' has is not a sound argument, as there is no evidence to prove such a bold and specific claim.