下列灯具中,电光源属于气体放电工作原理的是()。
A.碘钨灯
B.白炽灯
C.高压汞灯
D.信号桅的灯具
参考答案:C
给下列句子排序。
( ) I want five pears, please. How much are they?
( ) Good morning! Have you got any pears?
( ) How many pears do you have?
( ) Good morning! Can I help you?
( ) Yes, I have.
( ) They're ten yuan.
( ) Ten pears.
从商朝甲骨文演变到现今使用的汉字经历了三千多年,下图所示说明了文字演变的主要规律是由繁到简、从难到易。决定其如此演变的因素有
①古代帝王所创造 ②受书写工具影响 ③有利于交流传播 ④摒弃文化传统
A.①②
B.③④
C.①④
D.②③