The students ____ on a farm for ten days.Then they ____ to a factory.Though they ____ back at sch

The students ____ on a farm for ten days.Then they ____ to a factory.Though they ____ back at sch
The students ____ on a farm for ten days.Then they ____ to a factory.
Though they ____ back at school,they still remembered those farmers and workers.
A．have stayed; went; were
B．had stayed; go; are
C．have stayed; go; have been
D．had stayed; went; were