问题
选择题
Playing football and climbing are than watching TV. [ ]
A. more healthy
B. more healthier
C. much more healthier
D. much healthier
答案
答案：D
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Playing football and climbing are than watching TV. [ ]
A. more healthy
B. more healthier
C. much more healthier
D. much healthier
答案：D
其中L为抛物线y=x2上从O（0，0）到P（1，1）的一段弧，则I的值为（）。