Question

Last Saturday, we were walking along the street _____ a car suddenly knocked an old man over.
A when       B while       C as      D since

Answer 1

A

本題著重考察when與while和as的區(qū)別。when可以和延續(xù)性動(dòng)詞連用，也可以和短暫性動(dòng)詞連用；而while和as只能和延續(xù)性動(dòng)詞連用。 如：Why do you want a new job when you have got such a good one already？（get為短暫性動(dòng)詞,不可用while或as）你已經(jīng)找到如此好的工作，為何還想再找新的？ 本題從句中knock為短暫性動(dòng)詞，故選A正確。