题目

   Is there any  _______ to the time that I can keep the book? —Yes, you must return it within 2 weeks. A. number            B. length       C. limit      D. matter   答案：C下列正多边形中，能铺满地面的是 [     ]A.正五边形 B.正六边形 C. 正七边形 D. 正八边形