A、Because he likes learning. B、Because his hearing center is still immature. C、Because his ears are immature. D、Because he wants

A baby spends the first year of life learning to listen. A newborn child comes equipped with a finely tuned pair of ears, but he doesn’t yet know how to use them. A buzz of meaningless noise surrounds him. No one sound means more than any other. Unlike his ears, the hearing center of bis brains is still immature. As the baby grows, two things happen. First, he becomes better at picking out certain sounds. Second, he begins to remember them.
    This development is easy to see. If you make a loud sound near a day old baby’s head, you will not see any reaction. Only a check on his pulse or breathing rate will show a change. But just two weeks later, the same noise will make him jerk. He may even turn his head toward you, now the human voice means something to him. If he hears another baby crying, he may cry. By his fourth to sixth week, sounds like the doorbell or the closing of a door no longer surprise him.
What is actually happening is that he is starting to learn to listen. He can select certain sounds and memorize them. When he hears that sound again, he can match it with the one he has heard before. These skills are basic to all learning.
    At the same time these early hearing and language skills get under way, the child begins to practice making sounds. His first sounds are the discomfort sounds. These sounds are heard when he is not quiet or sleeping. These sounds mean nothing to him yet. To his mother they say he is wet, uncomfortable, or hungry.
    Within the baby’s first month, another sound appears: the comfort sounds. These are different from the discomfort sounds. As the child grows, his comfort sounds will use more of the vowels and consonants and rhythms which he will later use. These sounds will come together to form the first word. The special event will be long remembered by the proud parents.
Questions 16 to 18 are based on the passage you have just heard.
16. Why does a newborn baby have to spend the first year of his life learning to listen?
17. What’s a newborn baby’s reaction to a loud noise near him?
18. When does a baby begin to use more vowels and consonants?