Do you know how to make friends with a group of people? Let me tell you the steps about making friends with the group. Maybe it's helpful(有帮助的)to you.

    First, you need to know what kind of group they are. If people of the group are shy, never ask them “Why don't you talk?” “Why are you quiet?” or “Why do you look shy?”.They don't like such questions.

    Next, remember that each group is different. They may use different words, like different things or have different ways of “hanging out”.

    Then, the important thing is that you should try to be outgoing. If you are outgoing, you would become very popular. Remember, nobody wants to make friends with a shy person.

    Finally, find a right topic to talk with the group. For example, you can talk with them about the weather, the news, their hobbies or their school life.

根据短文内容，选择最佳选项。

    Here are some tips about how to keep healthy.

1) Healthy food is important. If you want to keep healthy, eat lots of fruit and vegetables. Don't eat much meat.

2) Water is important. Drink water every day. Milk is good for you, too. Don't drink sweet drinks.

3) Exercise is important. You can ride your bike or play soccer. Going swimming is a good idea.

4) Clean air is important. If you are free, you can go to the park and enjoy clean air.

5) Your teeth are important. You should brush your teeth twice a day.

6) Sleep is important, too. Go to bed early. Don't stay up late, or you will feel sleepy.

如图，在△ABC中，BD，CE分别为AC，AB边上的中线，BD⊥CE，若BD=4，CE=6，则△ABC的面积为（   ）