"Screen time" refers to time spent in front of a screen，such as watching TV，working on a computer，or playing on mobile phones.
   Most American children spend about 3 hours a day watching TV.Added together，all types of total screen time can be 5 to 7 hours a day.
   Computer，TV or mobile phones can help children with their education.But spending too much time on them is not good.For example，too much screen time can increase children's risk of putting on too much weight.
   Dr.Holland from America says screen time takes something important away from a child，including exercise，sleep and developmental activities. "Screen time is time that is not spent being physically active，and that children are missing out on learning valuable skills and developing their brains，" explains Dr.Holland.
   So the American Academy of Pediatrics （AAP） suggests the following screen time guidelines to children：
   Children under 2：Avoid all screen time.
   Children aged 2-5：Have no more than one hour of screen time each day.
   Children aged 6 and older：Set personal screen time limits（限制） to make sure their study，sleep and exercise won't be influenced.
   In 2019，the World Health Organization（WHO） set its own guidelines that are similar to AAP's.
   Cutting screen time down to 2 hours a day can be hard for children.But parents can set good examples first.They should spend less than 2 hours a day on screens.And parents should not watch TV during meals.Parents can play board games with their children or try other activities.In this way，they will live a more colorful and healthier life.

（1）How long do most American children watch TV a day？

About 3 hours a day.

About 3 hours a day.

（2）Where did Dr.Holland from？

America.

America.

（3）Who should avoid all screen time according to AAP？

Children under 2.

Children under 2.

（4）When did WHO set its own screen time guidelines？

In 2019.

In 2019.

（5）Who can set good examples first？

Parents.

Parents.