题干

在中央五套每周都有棋类节目,如棋类授课和评析节目,他们的棋盘都是竖直挂在墙上,棋盘是磁石制成的,而每个棋子都是一个小磁体,下列说法正确的是(  )
①小棋子共受到四个力作用;②每个棋子的质量肯定都有细微差异,所以不同棋子所受的摩擦力不同;③棋盘表面应选相对粗糙的材料;④如果某个棋子贴不上棋盘,总会滑落,肯定是其质量偏大.

A:①②④

B:①③④

C:①②③

D:②③④

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答案(点此获取答案解析)

C

同类题3

阅读短文,然后在文后表格内完成内容摘要,每空不超过三个词。

    We can remember some important times in our lives. Some things have become good memories. The memories are always in the corner of our mind.

    When I was in a kindergarten(幼儿园), I had many toys and friends. They made me laugh and cry. The teachers taught us many songs and games. We played all day. Although we did not know what learning was at that time, we were learning every day.

    When I was in a primary school, I was excited to learn school subjects. Nearly every subject caught my attention. However, my favorite subject was science. I remembered on the first day our science teacher told us the sun was like a big fire ball. We were quite surprised and kept our mouths open. We began to wonder at the secret of nature. Later many other things came to our ears. We began to learn carefully.

    When I was ten years old, I began to read newspapers, keep a diary, visit museums and make many friends. Every day was something new, interesting and exciting.

    Now I am in the middle school. Each day is new to me. I am still learning happily. It is like a journey to me. I have learned a lot, but there's still a long way for me to go. I hope to become a learned(有学问的) person some day.

Learning is____ a Journey

In a kindergarten

Although we know ____ about learning, we learned a lot

In a primary school

Among all the subjects, I like____ most.

At the age of ____

I began to keep a diary and visit museums.

In the middle school

I hope I won't stop____