氧瓶燃烧法测定有机元素时,瓶中铂丝所起的作用为()
A、氧化
B、还原
C、催化
D、支撑
参考答案:C, D
下列说法正确的是( )
A.本初子午线是地球仪上最长的经线
B.0°经线东侧为西经、西侧为东经
C.180°经线是东、西半球的分界线
D.向东数值递减的是西经
The boss demanded that all the work by 5 o'clock. [ ]
A.was finished
B.would be finished
C.be finished
D.finish