It's a long time_____we met lastA.so B.after C.since D.before请告诉我_英语解答

It's a long time_____we met last
A.so B.after C.since D.before请告诉我答案,顺便说明原因,谢谢

人气：365 ℃　时间：2020-03-19 21:43:36

解答

c,'so' cant leat a subordinate clause,"after" is as same as previous one."before" is obviously illogical.
just for your reference