问题补充：
I don’t doubt his advice is well worth.
A. that, to take
B. if, to take
C. whether, taking
D. that, taking
答案：
A. that, to take
B. if, to take
C. whether, taking
(答案→)D. that, taking
解析：句意：我不怀疑他的建议很值得考虑。在否定句和疑问句中，doubt
后面接that引导的宾语从句。be worth doing sth值得做某事
