It is many years we enjoyed ourselves on the great occasion.
A. since
B. that
C. before
D. when
网友回答
(答案→)A. since
B. that
C. before
D. when
解析：考查连词和固定句型：句意：我们很多年都没有在这样大型的场合玩的这么愉快了。A. since自从，B. that 做连词，没有含义，C. before在…前面，D. when当…时候，这里用了：It is+一段时间+since+从句的句型…，注意since后面的动词是延续性动词的时候，翻译成否定意思。选A。