By what age will children show preferences for particular playmates?

One potential problem of justifying past behavior in order to protect our self-esteem is that

a. people tend to become narcissistic. b. people distort reality and deny any negative information about themselves. c. it hinders people from learning from their past mistakes. d. it leads people to present themselves as being better than they really are.

The average level of age-graded problems a person can solve is used to determine the person's

a. chronological age. b. karyotype. c. mental age. d. genotype.