A、When they are with a baby-sitter. B、When they are with another baby. C、When they are with a strange adult. D、When they are wit

Recently a five-year study was conducted by the Centre for Childhood Development in Los Angeles, California, regarding the way babies react to different types of people. The findings of study suggest that infant children seem to be more comfortable around other babies than they are with strange adults.
    The results confirm the ideas of Dr. Richard Perelman, who has written many books about raising children. Dr. Perelman supports the findings of the study and adds that it is a sounder idea to keep children with other children, as in a day care centre, than it is to have children cared for by a baby-sitter.
    According to the results of the study, infants benefit from being in the company of other babies on a daily basis. Whereas some babies seem to show fear of strange adults, they are likely to reach out to try to touch an unfamiliar baby. The study even suggests that children as young as one year old can form friendships.
    Two of the children in the study were especially close. It was reported that if the children were separated for any reason they would start to cry. The only way to satisfy them was to allow them to be together. If the findings are true it may lead to an increase in the use of family-oriented day care centres where children can spend more time with each other and less time with adults.
Questions 16 to 18 are based on the passage you have just heard.
16. According to the study, when do babies feel the most comfortable?
17. How do babies react to unfamiliar babies?
18. What is the best way to care for babies?