Researchers claim to have found the first proof _______ getting a regular eight hours a night really does make you appear healthier and more attractive.

A．as

B．that

C．how

D．which

旅游者、旅游经营者、政府三方面的利益关系在市场上最终表现为()之间的矛盾。

A.旅游客源地与旅游目的地

B.旅游者市场竞争与市场治理整顿

C.旅游业的硬件与软件

D.旅游供给与旅游需求