----- I called you this time yesterday, but there was no answer. ----- Oh, I’m sorry. I ______ dinner at my friends’ home. A. have B. had C. was having D. have had 答案:C
下列实验现象描述正确的是
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A.
碘水中加入少量苯振荡,静置后上层颜色变浅,下层颜色变为紫红色
B.
红热的铜丝在氯气中燃烧,产生了棕黄色的烟雾
C.
碘化钾淀粉试纸遇到纯净的氯气变蓝
D.
在温度一定时,将2升的二氧化氮气体压缩至1升,气体颜色先变深,后变浅