— Sorry. I returned it to the library just now. Maybe it is still ____.
A:available
B:affordable
C:acceptable
D:valuable
一次函数y=-x的图象平分( ).
如图,PA,PB切⊙O于A,B两点,CD切⊙O于点E交PA,PB于C,D,若⊙O的半径为r,△PCD的周长为3r,连接OA,OP,则OAPA的值是( )