A、They generally hold bad feelings towards their birth parents. B、They do not want to hurt the feelings of their adoptive parent

When couples get married, they usually plan to have children. Sometimes however, a couple cannot have a child of their own. In this case, they may decide to adopt a child. In fact, adoption is very common today. There are about 60,000 adoptions each year in the United States alone. Some people prefer to adopt infants. Others adopt older children. Some couples adopt children from their own countries. Others adopt children from foreign countries.
    In any case, they all adopt children for the same reason: they care about children and want to give their adopted child a happy life. Most adopted children know that they are adopted. Psychologists and childcare experts generally think this is a good idea. However, many adopted children or adoptees have very little information about their biological parents. As a matter of fact, it is often very difficult for adoptees to find out about their birth parents, because the birth records of most adoptees are usually sealed.
    The information is secret, so no one can see it. Naturally, adopted children have different feelings about their birth parents. Many adoptees want to search for them, but others do not. The decision to search for birth parents is a difficult one to make. Most adoptees have mixed feelings about finding their biological parents.
    Even though adoptees do not know about their natural parents, they do know that their adoptive parents want them, love them and will care for them.
Questions 16 to 19 are based on the passage you have just heard.
16. According to the speaker, why do some couples adopt children?
17. Why is it difficult for adoptees to find out about their birth parents?
18. Why do many adoptees find it hard to make the decision to search for their birth parents?
19. What can we infer from the passage?