My understanding from ATPL theory days, is that anhedral is only used when lateral stability would otherwise be excessive even with the normal dutch roll protection measures in place (multiple yaw dampers etc). So, with swept wing jets, it is generally true to say that dutch roll is a potential problem at low IAS, whether anhedral or dihedral.
This understanding leads me to answer (a), on the basis that the mention of "anhedral" is a distraction that does not change the answer.
Of course, there could be an expert out there with a different & better reasoned answer...
Last edited by Oktas8; 9th March 2013 at 08:20.