that area is rich in natural gas,----------- this place isn't.

问题描述:

that area is rich in natural gas,----------- this place isn't.
A.unless
B.although
C.while
D.if

选C while是然而的意思,那个地方天然气很充裕,然而这个地方却不是,转折.unless是除非
aithough是尽管,不能放在句中,只能放在句首,if 是如果,是否的意思.