There is a boy _____________ in the river.
A:swim
B:swimming
C:to swim
D:swam
—Good idea.
— _____, but I felt very excited to see so many surprising animals.
pá shān hǔ
wō niú
____
hǎi shēn
lóng xiā
如图,PA、PB分别切⊙O于A、B,PA=10cm,C是劣弧AB上的点(不与点A、B重合),过点C的切线分别交PA、PB于点E、F.则△PEF的周长为( )