Tom was about to close the windows his attention was caught by a bird.A. whenB. ifC. andD.

问题补充：

Tom was about to close the windows his attention was caught by a bird.

A. when

B. if

C. and

D. till

答案：

(答案→)A. when

B. if

C. and

D. till

解析：考查固定句型，句义：汤姆正要去关窗户，这是他的的注意力被一只鸟吸引了was /were about to do 。。。+when。。。。正要去做。。这是突然。。。，把握关键词was about to close，所以A正确。