That was really a splendid evening. It's years I enjoyed myself so much.
A. when
B. that
C. before
D. since
网友回答
A. when
B. that
C. before
(答案→)D. since
解析：解析对时间状语从句的考查:由since引导的时间状语从句,如从句中的谓语动词是持续性动词,动作从结束时算起,本句表示的意思是“我已有多年没有玩得如此愉快”。如从句中的谓语动词是瞬间动词,动作从开始时算起,如：It’s three years since he joined the army.意为“他参军已经三年了。”根据句子的时态与句意,选D。