It has been proved that cockroaches (蝉螂) （） for several weeks even after their heads have been cut off.

A．had song contests
B．sang a new style of music
C．sang new words
D．made up the music as they played

A．they had found new work
B．they had worked long and hard during weekdays
C．they often lived alone, without their families
D．they were good at singing and dancing