Sally found that neither caffeine nor extraversion individually predicted problem solving; however, she found that they both worked together to predict problem solving. This is an example of what kind of an effect?
A) a true interaction
B) a suppressor
C) an evocation
D) a true mediation

A) a true interaction

Explanation: Problem solving includes using generic methods in an orderly manner to find solutions to problems. Some of the problem-solving techniques developed and used in philosophy, artificial intelligence, computer science, engineering, mathematics, or medicine are related to mental problem-solving techniques studied in psychology. To solve a problem one need to have an insight about the problem. Know what the problem is and then decide in the best approach to solve the problem.

can you explain it better

hello,

answer: a federal government has final authority on interstate/inter provincial  and international affairs, a confederation is one where the central/national government or authority is governing body what does not have final say over the same matters. hopefully this and i will try again if you don't like this answer : )

best of luck!