可以近似地认为弧柱的长度即为电弧长度。
参考答案：对
It's also just fun _____ people. I always have fun _____ it. [ ]
A. watching, to watch
B. watching, watching
C. to watch, watching
获得性掌跖角化病（PPK）不包括（）
A.更年期角化病
B.副肿瘤性PPK
C.炎症性PPK
D.弥漫性PPK
E.药物性PPK
