我国全面实施一对夫妇可生育两个孩子政策，可能带来一轮新的生育高峰．
It's sometimes too difficult to understand the voices of American film.
如图，⊙O过正方形ABCD的顶点A、B，且与CD相切，若正方形ABCD的边长为2，则⊙O的半径为（ ）
7b＋0.8b－6.5b＝____
