Answer:
B. Mary's sweater is missing.
Explanation:
Option A. Can't be correct, because the only reason you would put an apostrophe, to show possession after an S, is if that word ends in the letter S. In order for that sentence to be correct, you would need to put the apostrophe behind the S, because the word Jeff, does not genrally end in the letter S. Options C and D, don't have an apostrophe in general, so they are incorrect.
