问题
选择题
I don’t doubt_______ he took the first place in his class; but I do doubt_______ he will succeed in the end.
A．if; that
B．but; which
C．whether; whether
D．that; whether
答案
答案：D
本题考查动词用法。doubt在肯定句中用关系词whether/if，在否定句中用关系词that,故选D。