15．····························································································································································· 下列说法中正确的是 ( 　　)．

　　 (A)旋转对称图形一定是轴对称图形　　 (B)旋转对称图形一定不是轴对称图形

　　 (C)轴对称图形一定是旋转对称图形　　 (D)以上说法均不正确

14．····························································································································································· 下列图形中：①等边三角形；②正五角星形；③正方形；④圆.

属于旋转对称图形的有··········································································································· ( 　　)．

　　 (A)1个　　　　　　　　 (B)2个　　　　　　　　 (C)3个　　　　　　　　 (D)4个

13．····························································································································································· 下列情形不属于旋转的是 ( 　　)．

　　 (A)电风扇的扇叶在不停转动　　　　　　　 (B)时钟上的秒针不停地转动

　　 (C)单摆上转动的小球　　　　　　　　　　　　　 (D)笔直的铁轨上飞驰而过的火车

12．下列平面图形中，既是轴对称图形，又是中心对称图形的是··························· ( 　　)．

　　 (A)　　　　　　　　　　　 (B)　　　　　　　　　　　　 (C)　　　　　　　　　　　 (D)

11．下列图形中是中心对称图形的是······················································································· ( 　　)．

　　 (A)　　　　　　　　　　　 (B)　　　　　　　　　　　　 (C)　　　　　　　　　　　 (D)

10．如图，在□ABCD中，EF∥BC，GH∥AB，EF、GH相交于点O，那么图中除□ABCD外共有______个平行四边形.

9．在□ABCD中，∠A+∠C＝200°，∠A＝　　　　 ，∠B　　　　　 ．

8．如图，以△ABC的边AB、AC为边分别向外侧作等腰直角△ABD、△ACE，则将△ADC绕点A逆时针旋转______度可得到△ABE，此时CD与BE有_______________的关系．

7．如图，△ABC为等边三角形，D为BC中点，△AEB是△ADC绕点A旋转60°得到的，则∠ABE＝　　　 度；若连结DE，则△ADE为__________三角形．

6．一个正方形要绕它的中心至少旋转 　　　度，才能和原来的图形重合．