Question

I ________ my key to my office at home, so I had to wait until other teachers ________ to open the door．

1. A.
   had left; came
2. B.
   left; came
3. C.
   has left; came
4. D.
   left; would come

Answer 1

A
本題考查過去完成時和一般過去時的比較。leave my key這個動作明顯發生在had to wait之前，所以為過去的過去，用過去完成時；而come這個動作是出現在until引起的時間狀語從句中，應該用一般過去時代替過去將來時，所以答案為A項。