1.the music is often heard _______on the radio A.to play B.playedC.to be played D.playing

1.the music is often heard _______on the radio A.to play B.playedC.to be played D.playing
2.birds are seldom heard _______at night
A.sing B.singing C.to sing D.to be singing
3.being done能不能放句首作主语或状语