在下列句子的空缺处依次填入词语，最恰当的一组是（ ）①掐丝是一种非常 的工作。②这篇论文写得精准透彻，主要得力于作者 了大量资料。③人类对大自然的每一分破坏，都遭到了相应的报复，环境污染的威胁不亚于第三次世界大战，这绝不可 。

The line is engaged. I can’t _____ now.

.－It was snowing heavily last night. Is everyone here now－Yes,and _____ of us was late for school this morning.

I would like to have the experiment _____ right away [ ]

why didn’t you come yesterday—I __________, but I had an unexpectedvisitor.