写出下列单数名词的复数形式。
book —( ) foot —( ) family —( )
books，feet，families
—I want __________ in the __________ club.
—Sorry, sir. We have too many people in our club.
A．to be, swiming
B．be, swimming
C．be, swiming
D．to be, swimming
母线停电步骤？
