On what group was the first focus of research on posttraumatic stress disorder as the aftermath of traumatic events?

If two variables change consistently in relation to each other, they are said to ______

a. covary b. be independent c. represent equivalent groups d. be random samples

As children acquire representational skills, they gain the ability to

a. make their wishes come true. b. compare their performance to the performance of others. c. communicate about the past and create imagined experiences. d. move more freely in the environment.