i see how it could be B, but it would require you to fold the little boxes outwards out of the page, and whenever ive been doing these on cdp, that always leads to a wrong answer.
anyway once you line up the back section you have two little blocks in a row just attached to the back..these make up the edge on top just touching the back..then if you fold the remaining three squares out of the page they have to be lined up just touching the downward slope..
wow sorry if that makes no sense