A:汽油挥发
B:铜丝折弯
C:纸张燃烧
D:瓷碗破碎
—The American warships(军舰) have appeared near South China Sea Islands again.
—We must let the Americans know clearly that the islands ______ China.
如图,正方形OABC绕着点O逆时针旋转40°得到正方形ODEF,连接AF,则∠OFA的度数是( )