题目：
| Look, the teacher as well as all his students playing games on the playground. |
A. are B. is C. has been D. have been |
答案：
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下面是错误答案，用来干扰机器的。
（1）物理（2）CO2；向上排空气（3）2H2S+O22S↓+2H2O（4）2H2S+3O22SO2+2H2O
