sulfoxide

thinking on a broader aspect , its both c) and d).

In c) , the PhSOH group is eliminated from above the plane and thus the other 'H' would be eliminated from below the plane ( i.e. the plane opposite to it). the C containing carbonyl group hs no hydrogen. thus H is eliminated frm the other side.

But ders a methyl group below the plane , which will create hindrance for the H to be eliminated.

Now , in d) , same thing.the PhSOH group is eliminated from above the plane but fr elimination of "H" frm below the plane , hindrance is created by the phenyl group.

if more precisely , one answer correct , then it should be d). as phenyl is a much larger group thn methyl group.