题目

如图所示，AB为⊙O的直径，P点为其半圆上一点，∠POA=40°，C为另一半圆上任意一点（不含A、B），则∠PCB的度数为（ ）A. 50° B. 60° C. 70° D. 80° 答案：【答案】C【解析】根据平角定义,得∠BOP= -∠AOP= ,再根据一条弧所对的圆周角等于它所对的圆心角的一半,得∠PCB=∠POB=.解:∠POA=40°，∠BOP= -∠AOP= ∠PCB=∠POB=，故选C.I really don't know _________ this question.A.which to do B.which to answer C.what to do D.how to answer