Question

2．瑪麗在七歲時(shí)會(huì)騎自行車．（could，when ）
Mary could swim when she was five．

Answer 1

分析 Mary could swim when she was five．

解答 答案：Mary could swim when she was five．
表達(dá)的是過去的事情用一般過去時(shí)，表示能做某事用情態(tài)動(dòng)詞can的過去式could，后加動(dòng)詞原形swim，故Mary could swim．when引導(dǎo)的時(shí)間狀語從句，主語she，故was，故答案是Mary could swim when she was five．

點(diǎn)評 when引導(dǎo)時(shí)間從句用過去時(shí)，主句用過去進(jìn)行時(shí)：表示在從句動(dòng)作在過去發(fā)生時(shí)，主句的動(dòng)作在當(dāng)時(shí)也正在進(jìn)行．用于表示在過去有兩個(gè)動(dòng)作同時(shí)發(fā)生的情況，或者一前一后即在過去某動(dòng)作發(fā)生時(shí)或正在進(jìn)行中，又有一個(gè)動(dòng)作發(fā)生的情況（反之亦然），通常短暫性動(dòng)詞用過去時(shí)，持續(xù)性動(dòng)詞用過去進(jìn)行時(shí)．
When I got up，my mum was serving breakfast．
When I was having breakfast，my dad went out of home．