英语
Was it eight o`clock ______ you heard someone ______ at the door? A.when ;knock B.when;knocking C.that;knocking D.that;knock
选b。eight o'clock做先行词,在定语从句中做状语,所以用when,如果是强调句,需要加at。hear sb doing sth,听见某人正在做某事。
答案是C,这句子是It's that 的句子,只是前面颠倒了。后面的话,意思是八点的那时候听到在敲门,是那时的正在进行时,所以选择knocking.
B 比较合适。
答案B hear sb doing sth 听到某人正在做某事
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