The letters for the boss on his desk but he didn’t read them until three days later. (2012·天津，2)
A. were put
B. was put
C. put
D. has put
网友回答
(答案→)A. were put
B. was put
C. put
D. has put
解析：
句意为：给老板的那些信被放在了桌子上，但直到三天后他才读的。根据but后的“didn’t read”可知老板读信是发生在过去，所以信被放到桌子上应该发生在“读信”之前，也是过去的动作，与现在无关，所以排除D项；the letters与put之间为被动关系，故排除C项；而且the letters作主语，是复数，可排除B项。所以答案为A项。