Edward, you play so well. But I _____ you played the piano. [ ]

A. didn't know

B. hadn't known

C. don't know

D. haven't known

你认为性教育的作用应该是（）。

A.性教育能彻底根除性罪错，防止性犯罪

B.性教育会误导学生，教孩子学坏

C.性教育是提高个人素质和全民素质的途径之一

D.性教育是解决性领域中一切问题的灵丹妙药