题干

在一定条件下,甲、乙、丙、丁四种物质在一密闭容器中充分反应,测得反应前后个物质的质量如表所示.根据表中信息判断下列说法正确的是(   )

物质

反应前的质量/g

2

30

20

10

反应后的质量/g

m

39

5

16

A:该反应是化合反应

B:甲是该反应的催化剂

C:反应过程中乙、丙变化的质量比为3:5

D:丙可能是单质

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答案(点此获取答案解析)

C

同类题3

   ⑴在你班上谁更擅长科学,男孩还是女孩?Nowadays, girls start to show more interest in science, technology, engineering and math (STEM) subjects, according to a recent study by Cambridge Occupational Analysts (COA), UK.

    In the study, last year, ⑵over .20,000 students who were in their final year in high school were surveyed. The number of girls considering university courses in STEM subjects has been larger than that of boys. Over a fifth of the girls surveyed said they were considering related jobs, such as engineering and technology. Interest has also risen in mechanical (机械学的) engineering, electrical engineering and the sciences.

    ⑶对于英国的妇女,这是一个重要的改变。In the past, there were not nearly as many women as men studying STEM subjects or working in STEM related fields. Only 13% of people who graduated from university with STEM degrees were women. Now, there are about 22%. ⑷In the past, only one eight of the STEM jobs were held by women. This was partly because of the stereotype (刻板印象) that men are more suited to this work than women. Now it has been changed. Over 20% of the engineers are women in the UK.

    In fact, STEM subjects are fun and exciting. Studying science can benefit (使……受益) girls. “It opens girls up to fascinating careers,” Niki Yates, manager of GSK's UK Business, told The Daily Telegraph. She says ⑸it is important to encourage young women to do these jobs. They will receive higher pay in these areas. More women in work also helps the economy grow.

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