【问】 They asked me to have a drink with them.I said that it was at least ten years since I____a good drink.

A.had enjoyed B.was enjoying

C.enjoyed D.had been enjoying(全国高考英语试题，1988A)

正确答案为A(had enjoyed)。但是我认为C(enjoyed)也是正确的。

【答】 关于since从句的动词的时态，CGEL作了明确的说明：

“When the whole period is placed in past time，the past perfective or the simple past is usedin the since-clause.”(CGEL，P.1018)

“当整个时间段位于过去时间时，since从句可使用过去完成时或过去时。”下面是我们收集到的since从句使用动词过去时的例句：

1.Since the country (had) achieved independence，it (had) revised its constitution twice.(CGEL)

自从国家独立以来，已经两次修改了宪法。

2.It was ages since they last paid their bills on time.(CGEL)

自从他们上次按时付清帐单以来，已经过了很长时间了。

上面的高考题，如果选C(enjoyed)，则其结构与例(2)完全相同。可见，选C是完全正确的。

(参见since2条中的例句)