计算a⁴•${\left(\frac{1}{a}\right)}^2$的结果是（　　）

   The hottest place in the world is the Sahara Desert in Africa. But there are deserts in many other places: in America, in Asia and in Australia. In 1917 the temperature in Death Valley, in the United States, was over 48°C every day for six weeks. That's very hot!But deserts are not always hot. After dark, deserts are very cold.
   Not many animals and plants can live in a desert, because it doesn't rain very often. But one animal likes the desert — the camel. It has big feet to walk on the sand. It can live for a long time without water. Sometimes it doesn't drink anything for weeks — so it gets very thirsty! When it finds water it can drink 100 liters(升) at a time.