问题 选择题
如图所示,在x轴上方存在着垂直于纸面向里、磁感应强度为B的匀强磁场,一个不计重力的带电粒子从坐标原点O处以速度v进入磁场,粒子进人磁场时的速度方向垂直于磁场且与x轴正方向成120°角,若粒子穿过y轴正半轴后在磁场中到x轴的最大距离为a,则该粒子的比荷和所带电荷的正负是(  )

A.,正电荷

B.,正电荷

C.,负电荷

D.,负电荷

答案

答案:C

阅读理解

阅读下面短文,简要回答所给问题。

It was near Christmas during my first semester teaching at a new school.I loved my small special class more than any group I had taught in the past.They were hungry for knowledge and I was enjoying teaching.

Other teachers had told me that our children were from poor families and not to expect any child to bring a Christmas gift.In fact,I wasn't expecting any gifts.

Imagine my surprise when every child brought me a gift on the day before our holiday break.First,I got a much­loved stuffed monkey from a shy girl.I was told,“He is my favorite,but I love you and I want him to be with you,Miss Taylor.”How thrilled I was!

Next came a new set of Christmas tree lights that was “missing” from a mother's cupboard.

Finally,I came to one little boy's gift which I had never received.It was an old,dirty and broken Christmas story book.Just when I wanted to express my happiness,I was interrupted(打断)by the giver,“And see,it is new!It still has the price tag.”

When other children laughed at him,I stopped them and said,“Oh,books are good in that way.The story is always new if you have not read it before.Now,let's share one together.”Everyone listened quietly as I read the most wonderful Christmas story of my life.

I still keep those Christmas gifts.They always remind me of my lovely kids.

小题1:Why did the teacher like her small special class?

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小题2:When did the children bring their teacher gifts?

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小题3:Who sent a stuffed monkey to the teacher?

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小题4:Was the Christmas story book new?

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小题5:How did the teacher feel when she got the gifts?

多项选择题