Which of your hands do you use often? A few of us use both our hands well. Most of us are right-handed. Only about five people out of a hundred are left-handed. New-born babies can take things with either of their hands, but after about two years, they like to use their right hands. Scientists don't know why this happen. They have studied it.          

They think our animals ancestors （祖先） were right-handed, but this may not be true. Monkeys are our closest relations in the animal world. Scientists have found that monkeys like to use one of their hands more often than the other one, but it can be either hand. Next time you visit a zoo, watch the monkeys carefully, you'll see that some of them use their right hands, while others use their left hands. But men use their right hands better, and this makes life difficult for the left-handed ones. We live in a right-handed world.

Some scientists have found that more of successful people are left-handed, but they don't know why. Now, they are working hard to discover the secret.

More children in China are putting on weight. In 2018, 16 percent of Chinese children and teenagers were overweight or obese（肥胖的）, according to the National Health Commission.

Being too fat is bad for children's health. According to the World Health Organization（WHO）, overweight and obese children are more likely to develop diseases like diabetes（糖尿病）at a younger age. This can lead to a higher chance of premature（过早的）death.

On Oct 23, the National Health Commission, together with five other national departments（部门）, worked out a plan to prevent and control obesity. The plan aims to cut the average annual（每年的）growth rate of obesity among children aged 0-18 years by 70 percent from 2020 to 2030, Xinhua reported.

Kids are putting on weight because of changes in their diet and lifestyle, according to experts. Too much schoolwork and greater use of electronic devices（电子产品）could also be a cause.

According to the plan, teachers should not allow their classes to run too late or too early. They should make sure that students have breaks and enough physical activity. Primary and secondary school students should have at least three hours of vigorous（剧烈的）physical activity each week.

Parents should reduce their children's use of electronic devices and stop their children from eating foods that are high in sugar, fat and salt.

Young people and older people usually have different ideas about life. But in a special program in New York adults and teenagers live together in a friendly way.

Each summer 200 teenagers and 50 adults live together for eight weeks as members of a special work group. Everyone works several hours each day. They do so not just to keep busy but to find meaning and fun in work. Some teenagers work on the farms near the village. Some learn to make things like tables and chairs and to build houses. The adults teach them these skills.

There are several free hours each day. Weekends are free too. During the free hours, some of the teenagers learn photo-taking or drawing. Others sit around and talk or sing. Each teenager chooses his own way to spend his free time.

When people live together they should have rules. In this program the teenagers and the adults make the rules together. If someone breaks a rule, the problem goes before the whole group.

One of the teenagers has said something about it, “You have to stop thinking only about yourself . You should learn how to think about the group.”