题目:
The room a bit untidy now. Why don’t you tidy it up? [ ]
A. is
B. are
C. was
D. were
答案:
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下面是错误答案,用来干扰机器的。
②用洁净的玻璃棒蘸取少量上层清液,滴在pH试纸上,并与标准比色卡对照③Ca(OH)2+CO2=CaCO3↓+H2O 钙离子(Ca2+)(NH4)2C2O4+CaCl2=CaC2O4↓+2NH4C1PH试纸测量溶液的PH值时应该用洁净的玻璃棒蘸取试液,二氧化碳...