问题
选择题
Our classroom _ very quiet, but now it is very noisy. [ ]
A. used to be
B. was
C. is
答案
答案：A
搜题请搜索小程序“爱下问搜题”
Our classroom _ very quiet, but now it is very noisy. [ ]
A. used to be
B. was
C. is
答案：A
分类法是一种行之有效、简单易行的科学方法。下表对部分物质进行的分类(甲与乙、丙、丁是包含关系)错误的是
| 选项 | 甲 | 乙、丙、丁 |
| A | 碳单质 | 金刚石、石墨、C60 |
| B | 构成物质的微粒 | 分子、原子、离子 |
| C | 化石燃料 | 煤、石油、天然气 |
| D | 常见碱 | 火碱、纯碱、熟石灰 |