Please help me in this sentence
We are going to leave for Italy ……….. a week or so .
a) until b) by c) after d) in
the answer is (in) but why can't we choose (after) . what's the difference between (in) and (after) when they are used to indicate time ? how should i be sure that which one fits best (in) or (after)
please just tell me the difference and why i can't choose (after).