①Many people travel to varied places in the world by air. Usually it takes a long time, perhaps half a day, for passengers to stay in the plane. So airlines offer passengers food. But it is common that they feel bad about food taste. Do you agree?
②To solve this problem, airlines try hard to improve their food. They would like to do so because they don't want to lose customers.
③However, according to scientific research, a part of the reason why plane food tastes bad is that at high altitude (海拔) we can not taste things as well as we do on the ground. Also scientists have found that our noses become very dry even before a plane takes off. As the plane moves up, the change in air pressure reduces one third of the sensibility (感觉) of our taste buds(味蕾). So our taste buds become senseless. The sad face, however, is that our noses don't know it.
④All of these help explain why food on the plane tastes so bad. ____ Without doing so, the food would be tasteless.
⑤Now there are many researches 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 feelings about food taste.
⑥Though scientists try their 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 good is still hard for them.
