题目

在x轴上有两个点电荷，一个带正电Q1，另一个带负电Q2，且Q1=2Q2，用E1和E2分别表示两个点电荷所产生的场强大小，则在x轴上(    )A．E1=E2之点只有一个，该处的合场强为零B．E1=E2之点共有两处，一处合场强为零，另一处合场强为2E2C．E1=E2之点共有三处，其中两处合场强为零，另一处合场强为2E2D．E1=E2之点共有三处，其中一处合场强为零，另两处合场强为2E2 Children of America are getting fatter every time. 13% of the children at the age of 6 to 11 are overweight (too fat).When we look at the children's lives today in the USA, we can see the root of the problem----sports and foods. Young children like sports but they don't have enough around the start of high school. That's especially true for girls. Meanwhile, to make matters worse, schools are becoming much more interested in sports teams. So children are not able to get enough exercise just when they need it the most. There is also the food problem. Children get most of their calories at restaurants or parties or somewhere else away from home. They often drink too many Cokes. Parents have a lot of fears about telling a child he needs to lose weight-- they are afraid it will push a child into an eating disorder. Some parents fear that pushing children to lose weight means their children will think they're not good enough, or not loved because of their weight. Parents need to come to terms with(向…妥协) the fact that the family is very important to the children. The most useful program for children is called "family weight control". This is good news. Mom and Dad, even if they don't have weight problems, have to go through the same program as their children and learn how to get some exercise and how to eat healthily.【1】Why are American children getting fatter? The writer thinks ______________________.A. parents also have weight problem as their childrenB. children have less exercise and eat unhealthilyC. schools are more interested in sports teamsD. children drink too many Cokes【2】The writer wants to tell parents that _________________.A. overweight children are not loved by peopleB. family members can help overweight children a lotC. children are afraid to lose weight when they have toD. girls don't like to exercise【3】The writer thinks if mother or father is on the same program as their children, _______.A. their children will not eat betterB. it will make the children eat much moreC. "family weight control" will be successfulD. parents will feel sorry about themselves【4】Which of the following is NOT the root of overweight problem?A. Family weight control B. Less sportsC. Higher-calorie D. higher-fat foods.