I agree that this question is somewhat dubious (pretty dreadful actually), but I'm rather surpised that most contributors have ignored the torsional effects of dihedral. Dihedral causes the wing tips to be higher than the wing roots. So any drag acting at the tips tends to twist the wings leading edge up.
If we try hard enough we can find arguments that suggest that all four options are correct to some degree. But assuming all four factors apply to a given aircraft, then wing sweep is likely to be the most dominant in causing torsional loads on the wings. As stated in the previous post, if more than one option appears to be correct, students should pick that which they think is the most correct. In this case I'd go for sweep back.