The same life day by day is like eating white rice every day for your brain(大脑). Playing games with your mind(头脑) keeps your brains quick, and make your memory and powers of reasoning much better. Try the following fun and free activities to stimulate your brain.

 Use the opposite hand: If you are right-handed, become a lefty. Changing the hand you usually use can get your brain thinking in a different way.

Talk to yourself: Pick one hour a day to discuss something with yourself. Describe what you see, what you are doing, or what you are going to do. Talking while thinking is a great brain booster(助推器).

 Write down your dream: You can write out your wishes and goals(目标) and they can call your attention. Keep a pen and paper next to your bed. You can record your sleeping dreams with them. It is a fun way to get your brain thinking. Along with increasing memory, trying to unlock the secret behind your sleeping brain is one way to get to know yourself better.

 Walk on: Just like the body, your brain needs exercise, too. Walking can increase blood circulation(血液循环), which encourages blood vessels(血管) in your brain grow, raise energy production and throw away the waste. So walk anywhere at anywhere at anytime if possible.

以下关于生物变异的叙述，正确的是

在试管中加少量水，用嘴对着试管吹气，则试管中的____（选填“玻璃管”、“管中的水”或“水面上方空气柱”）会____而发声。小华用几只试管制作了试管乐器。调节水面高度后，用嘴贴着试管口吹气，能分别吹出“1（Do）”、“2（Re）”、“3（Mi）”等三个音调，则与这三个音调相对应的瓶子的序号是____.小华还发现，不用嘴吹，用筷子轻敲三只试管边沿，它也能发出不同的声音，这次发声的声源是____.

阅读下面短文，选择正确答案。

I have two friends. They are Bob and his sister Amy. Look! Bob

has a white T-shirt. He is not tall but fat. He is 10 years old.He

can ride a bike. Amy is the girl. She has a red skirt. She likes red

very much. She can fly a kite. She is 9 years old.

Oh! Look! The boy is me. I have a big mouth and long hair. I am

10 years old. I like swimming. I can swim very well. The little dog

is my friend, too. He can run and jump. He has big ears and a big

mouth. He is cute (可爱). I love him.

根据汉语提示完成下列句子