Which of these is not a recognized approach to federalism experienced during the history of the United States?

How can congress clarify parts of the constitution that are unclear?

Psychologists studying infant memory want to determine at what age babies can remember specific events. an experimenter uses several puppets to demonstrate a series of actions while the infant watches. after a delay, the experimenter records how many of the actions the child imitates when playing with the puppets. what is the dependent variable?

Which term describes a possible explanation of, or answer to, a scientific question that is based on prior knowledge or research and that is testable?