The largest bird that cannot fly also happens to be the largest living bird in the world. This is the huge North African ostrich  . When the male is fully grown, he reaches a height of nearly eight feet and many weigh close to three hundred pounds. His wings are very small and the wing feathers are very soft, and therefore he does not fly. You have probably heard the old saying about "the foolish ostrich burying his head in the sand". Well, the ostrich is not nearly as foolish as he is said to be. In the daytime, when the hen is sitting on the eggs, she does not want to be seen; instead of sticking her long neck up into the air, she bends   her neck and head down. That way, she can best protect the eggs and herself. Because the ostrich cannot fly up into the air to escape from danger on the ground, he has to remain alert at all times. Luckily, he has very good eyesight and hearing, so he can stop danger in time to run away. The ostrich can run so fast that it almost seems as if he is flying. Sometimes, when a person has a small appetite  , we say that he "eats like a bird". Of course, that bird is not the ostrich! An ostrich will eat anything under the sun. When an ostrich died in a zoo, scientists cut it open to see what he had eaten. Here are some of the things found in its stomach: three pieces of wood, part of a film roll, a French coin, four pennies, and so on. Ostriches bury their heads in the sand because they   _  .
are too lazy to do anything can avoid being attacked can relax by doing so are very shy
Question: The largest bird that cannot fly also happens to be the largest living bird in the world. This is the huge North African ostrich  . When the male is fully grown, he reaches a height of nearly eight feet and many weigh close to three hundred pounds. His wings are very small and the wing feathers are very soft, and therefore he does not fly. You have probably heard the old saying about "the foolish ostrich burying his head in the sand". Well, the ostrich is not nearly as foolish as he is said to be. In the daytime, when the hen is sitting on the eggs, she does not want to be seen; instead of sticking her long neck up into the air, she bends   her neck and head down. That way, she can best protect the eggs and herself. Because the ostrich cannot fly up into the air to escape from danger on the ground, he has to remain alert at all times. Luckily, he has very good eyesight and hearing, so he can stop danger in time to run away. The ostrich can run so fast that it almost seems as if he is flying. Sometimes, when a person has a small appetite  , we say that he "eats like a bird". Of course, that bird is not the ostrich! An ostrich will eat anything under the sun. When an ostrich died in a zoo, scientists cut it open to see what he had eaten. Here are some of the things found in its stomach: three pieces of wood, part of a film roll, a French coin, four pennies, and so on. Ostriches bury their heads in the sand because they   _  .
A. are too lazy to do anything
B. can avoid being attacked
C. can relax by doing so
D. are very shy
Answer: