word choice - "A number of positions , ___of which were exactly what he was looking for."

Mr. A was offered a number of positions in the company, _____ of which were exactly what he was looking for.

1) few
2) both
3) none
4) all

The correct answer for this question is 3 - none.

As for me, of the two answers, none and all, what is more natural for the above sentence is very confusing to me.

Can you explain why the "all" above does not match the answer?