你好,同学
正确答案：选D.since
即：That was really a splendid evening.It's years ( since ) I enjoyed myself very much.
翻译：那确实是一个极为满意的晚上,我好几年没有这么快乐了.（自从我上次快乐到现在有几年了.）
解析：当有It's years...或It has been...时,用连词since 引导,表示自从...已经有...时间了.
希望能帮到你,祝更上一层楼O(∩_∩)O
有不明白的请继续追问,可以详谈嘛(*^__^*)