When I got home, I realized I ________ my keys at school.

1. A.
   had left
2. B.
   left
3. C.
   leave
4. D.
   would leave

 －You look worried. What’s the matter?

－I _________ my keys at school. How can I get into the house?

A. kept                           B. left                           C. forgot                      D. took

When I got to school, I realized that I          my book at school.

A. leave   B. would leave    C. have left        D. had left