— Excuse me, have you seen _______ umbrella here?— Yes. Is it _______ beautiful blue one? I saw it here just now.
A:an, the
B:an, a
C:the, the
D:the, a
如图点P为弦AB上一点,连接OP,过P作PC⊥OP,PC交⊙O于点C,若AP=4,PB=2,则PC的长为()
随着科教兴国战略的实施,教育越来越成为综合国力竞争的决定性因素。( )