I regret ___ harder in the past two years.

A．not having studied

B．having studied

C．having not studied

D．not being studied

依照《安全生产法》的规定，生产经营单位( )与从业人员订立协议，免除或者减轻其对从业人员因生产安全事故伤亡依法应承担的责任。

A．可以

B．经有关部门批准可以

C．一般不得

D．不得