B7 时态和语态
热点7·4
①(2012·天津卷)The letters for the boss ________on his desk but he didn't read them until three days later.
A．were put B．was put C．put D．has put
答案 A [句意：给老板的信放在他的桌子上，但他三天后才读。考查动词的时态、语态和主谓一致。根据语境及but分句的时态可知前半句也应该用过去时，故排除D项；又因为letters同put之间为被动关系，故排除C项；根据主语letters为可数名词复数可知B项不正确，所以选A项。]
②(2011·北京卷)Experiments of this kind ________in both the U．S. and Europe well before the Second World War.
A．have conducted B．have been conducted
C．had conducted D．had been conducted
答案 D [句意：早在第二次世界大战之前，这种实验就在美国和欧洲进行过了。根据句中的时间状语before the Second World War可知，应该用过去完成时态，故排除A、B两项。再根据谓语动词conduct
