问题
单项选择题
计算CO2中氧元素的质量分数，正确的表达式是（）。
A.A
B.B
C.C
D.D
答案
参考答案：C
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计算CO2中氧元素的质量分数，正确的表达式是（）。
A.A
B.B
C.C
D.D
参考答案：C
| 完形填空。 Jack Black has a big __1__. His grandfather and grandmother __2__ in England. They are at home. Their __3__ are Nick Blac  k and Anna Black. But Jack's parents are in China. Jack's __4__ is an English teacher. He works in a middle school. Jack's mother __5__ a teacher. She is a doctor (医生). Jack and his __6__ Mary are students. They go to the same (同一个) __7__ in Beijing. Jack is __8__ Class One, Grade Seven. At school Jack has __9__ good friends. They are Lin Feng, Li Lei, and Sun Weiming. Mary has many good friends, too. They _10__ their school. | ||||
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