问题
单项选择题
No adults would like to admit that they are weaker than children to solve sticky and puzzling problems.
A．to solve about
B．solve
C．in solving about
D．in solving
答案
参考答案：D
解析：[分析] 固定搭配 be weak at/in sth．或be weak in doing sth．表示：……较弱，不擅长……；或不擅长做某事。所以答案为D。
(i=1，2，…，n)．求