Which of the following concepts explains why preoperational children can seem exasperatingly selfish or uncooperative at times?

According to surveys in which teens report their increasingly intimate sexual activities,

A) boys and girls follow the same sequence of activities at about the same age. B) girls report the same sequence of activities as boys, but a year later. C) girls, who reach puberty earlier than boys, become involved in sexual activity earlier too. D) the sequence of sexual activities is shorter for boys, who skip over some of the steps that girls report.

In the experiment by Hunziker and Barr (1986), mothers in Group A were instructed to carry their infants for at least three hours a day, while the mothers in Group B were not given any special instructions. What were the results?

a. There were no differences between Group A and B infants. b. Both groups of infants cried the same number of times, but Group A infants cried half as long Group B infants. c. Group B infants learned to soothe themselves and cried less than Group A infants. d. Group B infants cried many more times during the day than Group A infants.