题目

如图，OA，OB是⊙O的两条半径，且OA⊥OB，点C在⊙O上，则∠ACB等于（ ）A. 20° B. 25° C. 35° D. 45° 答案：【答案】D【解析】根据圆心角和圆周角的关系，即可解答.解：∵OA⊥OB，∴∠AOB＝90°，∴∠ACB＝∠AOB＝45°.14、I don’t think ___ possible to travel around the world without any modern equipment． A．this        B．that         C．its            D．it