题目

The two sides have finally___________, though some small differences still exist. A. made a decision            B. reached an agreement C. settled down               D. broken up 答案：B 解析: A项意为“做出决定”，B项为“达成一项协议”，C项为“定居”，D项为“破译”，故根据题干中“two sides have finally”需填入“达成协议”。如图，PT是⊙O的切线，T为切点，PA是割线，交⊙O于A、B两点，与直径CT交于点D．已知CD=2，AD=3，BD=4，那PB=    ．