Topscore #78 asks which of the following can be meso and the choices are a)cis-1,2-cyclopentanediol, b)trans-1,2-cyclopentanediol, c)2,3-dihydroxybutane, d)A&B, and e)A&C.

Obviously B is incorrect. They say the answer is E but I think it should be only C. For cyclic compounds i was taught that the only way they can be meso is for the substituents to be cis and on odd # carbons. Because if they are on even # carbons one is axial and one is equatorial. What do yall think?

you just answered your own question. Look at choice A again. Cis OH-groups on cyclopentane (5 Carbons). There is a line of symmetry so it is a meso compound.

Yes, but one substituent is on Carbon 1 and one is on Carbon 2, which makes one axial-like and one equatorial-like.

this could be completely wrong but i think because it is a pentane, not a hexane, it doesn't undergo the chair conformations and you therefore wouldn't have to take axial or equatorial into account for this...they are all on the same plane. but again, im not completely sure..

since it is a cis isomer, the two -OH groups would be either ax/ax or eq/eq. Trans -OH on the 1 and 2 carbon would make it ax/eq.