题目内容：
根据下面内容，回答题： Only one animal can walk 200 miles without stopping once to rest. It would take a person two days and two nights to walk this far, and only one man has ever done it without stopping. What amazing animal has such endurance? The camel! The camel is well known for something else, too. It can cross an entire desert without a single drink of water. Its body is built in a special way to help it store water and food.
A person has just one stomach, but a camel has quite a few. Within each stomach are layers and layers of cells. These ceils are like tiny water balloons, storing liquids until the camel needs them.
When the camel drinks, the cells grow larger and larger. For a whole week, they can keep the animal's thirst away by sending water to all parts of its body.
And did you ever wonder why the camel has a hump? The hump is a storage place for fat.
Because it has this storage area, the camel does not need to eat very often. When the animal needs energy, the layers of fat serve as fuel to keep it going on the long, hot days in the burning sun.
The camel has one other gift that makes it well suited to arid regions. This gift is its amazing nose. A camel can smell a water hole from miles away!
When a camel moves it sways from side to side like a ship on a wavy ocean. Because of this swaying motion, the camel has been called the "Ship of the Desert. "
The camel's hump is a storage place for________. A．muscles
B．extra water
C．body sugars
D．fat
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