I ____ English at the Teacher’s College, but I’m now ____ in a m

I ____ English at the Teacher’s College, but I’m now ____ in a middle school.
A、teach; teaching
B、teaching; teach
C、taught; teaching
D、teaching; taught
【正确答案】：C
【题目解析】：根据now,可推断前一空为过去式，因此要用过去时态，后一句为现在时，用现在时态，be doing