6.In Antarctica(南極),when spring comes,ice begins to melt,and the sun stays in the sky all night long.
In the brightly world,the large gray head of a Weddell seal (威德?tīng)柡1?nbsp;appears through a crack (裂縫) in the ice.The seal takes several deep breaths,and then she opens her mouth,turning her head from side to side.With her teeth,she gets rid of bits of ice.Seals are mammalOs(哺乳動(dòng)物),and they need to breathe air,for which Weddell seals use their teeth to make sure their breathing holes stay open.
The seal makes the hole bigger,and when she can fit her large body through it,she jumps out onto the ice-she is getting ready to have a baby.On the ice shelf,the seal gives birth to a baby.The baby is about three feet long and is covered with thick fur that protects it from the cold wind.The baby drinks its mother's milk and grows quickly.With a few weeks,it is more than six feet long.Under the seal's skin is thick layer of fat called blubber,which keeps the seal warm in its frozen world.
When the baby seal is about two weeks old,it begins to dive with its mother.They slide through the breathing hole into the water below the ice,where the baby seal learns to swim,diving deeper and deeper.In order to stay underwater,it must learn to hold its breath and control its heart rate.
Below the ice,the sun shines brightly through the hole.Finding the opening to breathe is easy,but getting back onto the slippery ice can be difficult for a young seal.With practice and its mother's help,the baby seal soon feels at home both on the ice and under it.
The young seal spends more and more time below the ice,where it learns to hunt for food.When the young seal is about two months old,it will have to feed itself independently.When it becomes an adult,it will swim farther out in search of food,but it will always live on or under the ice.
71.Paragraph 2is mainly aboutD.
A.the function of Weddell seals'teeth
B.the living conditions of Weddlel seals
C.how Weddell seals move under the ice
D.how Weddell seals keep their breathing holes open
72.According to Paragraph 3,the baby sealD.
A.grows slowly
B.is still short after a few weeks
C.is born under the ice
D.is covered with thick fur
73.The baby seal begins learning to swim and dive when it is aboutB.
A.two days old B.two weeks old
C.two months old D.two years old
74.For a young Weddell seal,C.
A.its father's help is important
B.getting onto the ice shelf is easy
C.finding the breathing hole is easy
D.learning to hunt for food is unnecessary
75.The text is mainly aboutA.
A.Weddell seals'life
B.a(chǎn)nimals on and under the ice
C.how Weddell seals keep warm
D.what the winter in Antarctica is like.