1)she isn't singing2)my sister is slipping3)is father drinking tea?4)are your parents drinking tea?5)I'm not slipping 6)she isn't sitting at the table7)we are doing an exercise8)we aren't bathing 9)they are playing in the yard10)Nina and Ann are wishing floor11)Kolya is helping his mother 12)are you helping your farther?13)my sister is reading an interesting book14)they are going to school15)are you going to school?16)is he working?