It is most instructive lecture that I since I came to this school.
A. attended
B. had attended
C. am attending
D. have attended
网友回答
A. attended
B. had attended
C. am attending
(答案→)D. have attended
解析：从时间状语 since I came to this school可以看出要与现在完成时连用。故选D。句意，这是自从我来到这个学校以来听过的最有教育意义的讲座。