Thestudents____onafarmfortendays.Thenthey____toafactory.Thoughthey____backatschThestudents____onafarmfortendays.Thenthey____toafactory.Thoughthey____backatschool,theystillrememberedthosefarmersandworkers.A．

　　Thestudents____onafarmfortendays.Thenthey____toafactory.Thoughthey____backatsch

　　Thestudents____onafarmfortendays.Thenthey____toafactory.

　　Thoughthey____backatschool,theystillrememberedthosefarmersandworkers.

　　A．havestayed;went;were

　　B．hadstayed;go;are

　　C．havestayed;go;havebeen

　　D．hadstayed;went;were