1.否定句:I am not doing my work.疑问句:Are you doing you work?Yes ,I do.No,I do not 2 .否定句:Tom is not singing a song in the room.疑问句:Is Tom singing a song in the room Yes ,he is.No ,he is not.3.否定句:Kate and Lily are not writing letters now .疑问句:Are Kate and Lily writing letters now Yes ,they are .No they are not.