I hear them singing a song.(保持意思不变)I hear ____ they ____ ____ a song

I hear them singing a song.(保持意思不变)I hear ____ they ____ ____ a song
I hear them singing a song.(保持意思不变)
I hear ____ they ____ ____ a song

I hear them singing a song.(保持意思不变)I hear ____ they ____ ____ a song
that, are singing

I hear that they are singing a song.我听见他们正在唱歌。

i agree