根据《中华人民共和国渔业法》的规定，在（）建闸、筑坝，对渔业资源有严重影响的，建设单位应当建造过鱼设施或者采取其他补救措施。

A.渔业资源保护区

B.鱼、虾、蟹洄游通道

C.鱼、虾、蟹栖息地

D.重点渔业经济区

The reason _____he was absent was _____ he was ill and unable to go to school.

A．which; that

B．why; because

C．which; because

D．why; that