问题补充：
They when they heard him confess his fault.
A. had been surprising
B. were surprising
C. were surprised
D. had been surprised
答案：
A. had been surprising
B. were surprising
(答案→)C. were surprised
D. had been surprised
解析：时间状语是过去时态，主句也应用过去时态，从句中heard是一般过去时态。
