问题
选择题
Can you tell me what made him so ______? [ ]
A. sadly
B. sad
C. sadder
D. more sadly
答案
答案：B
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Can you tell me what made him so ______? [ ]
A. sadly
B. sad
C. sadder
D. more sadly
答案：B
，其中L是从A（0，0）沿y=sinx到点B（π／2，1）的曲线段，则其值是：（）