Verified answer

The first is a question and thus ends with a question mark.

Yes, those are both grammatically correct English sentences. Awkward, but not incorrect.

To be frankly honest, they are gramatically incorrect.

a. Can it be that he has taken my book?

b. It cannot be that she is using your pen.

When in doubt, do not use apostrophes/shorthands, always type in formal English when writing homeworks and essays and exams etc

Hope it helped. :-)