Food aid______ is not enough to ______ the problem _______ now.
A:only; solve; discussed
B:alone; solving; being discussed
C:merely; solving; being discussed
D:alone; solve; being discussed
判断题
AB为⊙O直径,BC为⊙O切线,切点为B,CO平行于弦AD,作直线DC.
①求证:DC为⊙O切线;
②若AD•OC=8,求⊙O半径r.