一Did you notice a strange man just now?

一Sorry，I ______of something else．

A．thought    B．was thinking

 C．have thought D．had thought

—You may find the key to the math problem on page 107．
—Ah, it's so simple. I wonder why I _____ of that．

The professor kept telling us that the future _____ to the well-educated and I kept wondering where I _____ of it.

A. would belong; heard                 B. belonged; had heard

C. was belonged; heard                  D. was belonging; had heard

—Is there anything wrong, Bob? You look sad.

—Oh, nothing much. In fact, I __________ of my friends back home.

A. have just thought      B. was just thinking

C. would just think D. will just be thinking

—You may find the key to the math problem on page 107.

—Ah, it’s so simple. I wonder why I _____ of that.

A. hadn’t thought  B. haven’t thought C. didn’t think D. wasn’t thinking