With respect to intelligence testing in adulthood, scores on items measuring fluid intelligence with age and scores on items measuring crystallized intelligence with age.

a. decrease; increase
b. increase; decrease
c. decrease; decrease
d. increase; increase

A. decrease; increase                              

Explanation:

Fluid intelligence: The term fluid intelligence refers to the capability of an individual to think logically or rationally and to solve problems related to unexpected situations, and is considered to be as independent in acquiring knowledge. The propensity of fluid intelligence is believed to decrease with age. It is directly associated with innovation and creativity.

Crystallized intelligence: The term crystallized intelligence refers to the tendency of an individual to accumulate facts, skills, and knowledge which is considered to be required throughout the life of an individual. According to intelligence testing in adulthood, it is said that the crystallized increases with age.

answer; researchers typically cannot control people's sexual behaviors as would be necessary in an experiment;

answer; /// all of the above;