Question

两道英语选择题，请详细解释

1.-----We did not see him at the lecture yesterday.
------You______him,since I went to an international conference with him,
B.can't have seen C.couldn't see
2。Of the 9500 drivers____since the beginning of the year,23% were found lacking in knowledge about traffic rules.
A.tested C.having been tested D.to have been tested

Answer 1

1、B
这是对过去的猜测，所以要用过去完成时。
2、C
在今年初对司机的测验中，发现百分之23的司机缺乏交通规则的知识。
首先司机是被测验，而不是自己测验，因此要用被动语态。又要表示被测验这个动作是在发现之前，排除A.这句话的原话是The 9500 drivers had been tested since the beginning of the year,and 23% Of the 9500 drivers were found lacking in knowledge about traffic rules.
这是两个句子并列，但是两个句子的主语有相似之处，可以采用独立主格结构

Answer 2

1C
2C过去完成时，被动形式，首先这些司机是被测试的，当后面是since时前面一般用完成时，并且前面这个句子只是从句，用having，所以选C

Answer 3

having been done 不是不能作后定的吗？否则这里的having been tested 作什么成分啊