Question

【题目】Tom was about to close the window his attention was caught by a bird.

Answer 1

【答案】when
【解析】句意：汤姆正要关窗户，这时他的注意力被一只鸟吸引住了。“Sb. was about to do sth. when ..”是固定句型，“某人正要做某事，这时突然……”。故填when。