As we all know, there is very short of water in lots of areas in Africa. However, there is a magical tree which can help to solve the water problem. It is called the “sacred（神圣的）tree of Africa”—baobab tree（猴面包树）.

A baobab tree is huge like an upside-down carrot. It can grow so large that it requires more than 40 people holding hands to circle it. Actually, most baobab trees are not very tall, only about ten meters.

A baobab tree is full of treasures. It is said that if everyone in Africa had a 10-meter-tall baobab tree, it would solve more than 50% of their food problems. In hot Africa, water is the most needed. When the rainy season comes, the baobab tree starts to hold water in its body. The baobab tree is said to be the most water-holding tree. It can hold thousands of kilograms of water in its body. Local people usually cut a hole in the tree with a knife and get clean water from it. The baobab tree leaves are a bit like spinach（菠菜）leaves. True to its Chinese name, the fruit of the baobab tree tastes like bread. But it’s not like bread with cream. It tastes dry. Local people seldom get stomach problems because of eating it.

Baobab trees are not only useful for humans, but for animals in nature! Their fruit can be good food for monkeys, lizards and other African animals. Their leaves can also be eaten to get enough water.

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Inventions play an important part in our lives. They open the door to a new world for us and change the way we live. Humans have been inventing from the beginning of time. Some of the most famous inventions are so common in our everyday lives that we no longer think of them as inventions. Here are some inventions from different centuries.

	In 1876, Alexander Graham Bell built the first telephone that transmitted (传输) the human voice by electricity.
	There are many important events (事件) in the the history of computers. In 1936, Konrad Zuse built the first freely programmable computer.
	Eli Whitney patented (获得专利) the cotton gin on March 14, 1794. The cotton gin is a machine that separates unwanted materials from cotton after it has been picked.
	Barthelemy Thimonnier invented the first sewing machine in 1830. Elias Howe patented and improved sewing machine in 1846.
	Penicillin was first noticed by a French medical student, Emest Duchesne, in 1896. It was rediscovered by Alexander Fleming in 1928.

Do you know why different insects (昆虫) or animals have their special colors? These colors can help them stay away from other dangerous animals.

Some birds like eating locusts, but ________. Why? It is because locusts change (改变) their colors with the plants. When plants are green, locusts look green. When plants are brown, locusts change to the same color. But not all insects can change their colors. It’s easy for other animals to see them. So they have to come out only at night.

If you study animal life, you will know the change of color is also important for animals to live in the wild (野外). Bears, monkeys, and other animals live in the mountains. Others can’t see them easily because they have the color much like the trees.

What about sea life? Octopus can send out something black when it faces danger and quickly (飞快地) swim away. It is not strong, but it can save itself in this way.