阅读理解。
Christmas (圣诞节) is December 25. It's the most important holiday in America.
People like to send Christmas cards to their friends and they buy gifts for their family and friends before
Christmas.
Christmas Day is a day for family reunion (团聚). The family come together and sit down to have a meal
in the afternoon. On Christmas Day people go to church (教堂) to listen to Christmas Carols (颂歌). Children
are very happy on that day, and they can get a lot of gifts.
1. ________ is the biggest festival in America.
A. Christmas
B. New Year
C. Thanksgiving Day
D. Teachers' Day
2. Many people can get some ________ before Christmas.
A. work
B. cards
C. new clothes
D. cards or gifts
3. The family often have ________ together in the afternoon on Christmas Day.
A. a meeting
B. a meal
C. a ball
D. match
4. Children like Christmas Day very much, and they can ________.
A. get many gifts
B. watch TV all day
C. sing Christmas songs
D. go to the concert
5. Children like Christmas Day very much, and they can ________.
A. get many gifts
B. watch TV all day
C. sing Christmas songs
D. go to the concert
，处在水平向右的匀强电场中，一质量为
的带电小球从槽的右端A处无初速沿轨道滑下，滑到最低位置B时，球对轨道的压力为
.求：
