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To solve this problem, airlines try hard to i their food. They would like to do so because they don't want to lose c.

However, according to scientific research, part of the reason why plane food tastes bad is that at a high altitude (海拔，高度) we cannot taste things as well as we do on the g. Also scientists have found that our noses become very dry even b a plane takes off.

As the plane moves up, the change in air pressure (气压) reduces one third of the sensitivity (敏感性) of our taste buds (味蕾). So our taste buds become senseless. The sad fact, however, is that our noses don't know it.

All of these help explain why food on the plane tastes so bad. They a help explain why airlines choose to offer passengers salty and spicy (辛辣的) food. W doing so, the food would be tasteless.

Now there are many studies on this. According to one of them, some volunteers are asked to lie with their feet higher than their heads for weeks. And scientists write down their f about food taste.

Though scientists try t best, it is not as easy as they thought. Because they can't deal with the special environment successfully, such as the change in air pressure, making food taste g is still hard for them.

Nobody knows who first invented it, but the umbrella was used in very ancient times. Probably the first to use it were the Chinese, back in the eleventh century BC.

We know that the umbrella was used in ancient Egypt and Babylon as a sunshade. And there was a strange thing connected with its use: it became a symbol of honor and power (权力). In the Far East in ancient times, the umbrella was allowed to be used only by those in high office or byroyal people such as the kings or queens.

In Europe, the Greeks were the first to use the umbrella as a sunshade. The umbrella was in common use in ancient Greece, but it is believed that the first people in Europe to use the umbrella as protection against the rain were the ancient Romans. During the middle ages in Europe, the use of the umbrella almost disappeared. Then it appeared again in Italy in the late sixteenth century. And again it became a symbol of power.

Umbrellas have not changed much in style during all this time, though they have become much lighter in weight. It wasn't until the twentieth century that the umbrellas for women began to be made in all kinds of colors.

There are many6of making pocket money by kids themselves. First of all, they learn the7of money by working hard so that they will not waste any. Secondly, they learn to8money to buy things they need or want, such as books, pencils, movies and even clothes they like. Thirdly, they learn to9the daily life problems by helping their parents or others. Making pocket money is10for children when they grow up. That is why parents encourage their kids to make pocket money.

—Good idea! Let's go.

—No. He's been looking forward to _______ the Pyramids.

—About two thousand. A number of them _________ from England.

—They are wonderful, but I've read             of them.

—________.

—Yes. He always      30 minutes taking a walk after supper.