The blue sky of the holiday brochure was such a ______this rainy March day.

A．compare with

B．compare to

C．contrast to

D．contrast as

下列方法中，鉴别氮气、氧气两瓶气体的最佳方法是

A．测量气体的密度

B．测量气体的溶解性

C．称量两瓶气体的质量

D．用燃着的木条分别伸入气体中