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问题 不定项选择

甲、乙两个物体都做匀速圆周运动，转动半径比为3：4，在相同的时间里甲转过60圈时，乙转过45圈，则它们所受的向心加速度之比为 [ ]

A．3：4

B．4；3

C．4：9

D．9：16

答案

答案：B

选择题

有关氧气的叙述错误的是（　　）

A．氧气是一种化学性质比氮气活泼的气体

B．氧气能够跟许多物质发生化学反应

C．在氧化反应中都有热量放出

D．物质跟氧反应都能发光发热
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单项选择题

A proven method for effective textbook reading is the SQ3R method developed by Francis Robinson. The first step is to survey (the S step) the chapter by reading the title, introduction, section headings, summary and by studying any graphs, tables, illustrations or charts. The purpose of this step is to get an overview of the chapter so that you will know before you read what it will be about. In the second step (the Q step), for each section you ask yourself questions such as "What do I already know about this topic" and "What do I want to know" In this step you also take the section heading and turn it into a question. This step gives you a purpose for reading the section. The third step (the first of the 3 R’s) is to read to find the answer to your questions. Then at the end of each section, before going on to the next section, you recite (the second of the 3 R’s) the answers to the questions that you formed in the question step. When you recite you should say the information you want to learn out loud in your own words. The fifth step is done after you have completed steps 2, 3 and 4 for each section. You review (the last of the 3 R’s) the entire chapter. The review is done much as the survey was in the first step. As you review, hold a mental conversation with yourself as you recite the information you selected as important to learn. The mental conversation could take the form of asking and answering the questions fromed from the headings or reading the summary, which lists the main ideas in the chapter, and trying to fill in the details for each main idea.

The SQ3R method consists of（）steps.

A. three

B. four

C. five

D. seven
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