Aresearcher working with college-age football players is conducting a longitudinal study to examine an athlete's decline in on-the-field performance as the athlete ages. what type of development would the researcher most likely be studying?

I believe the answer is: physical development

In longitudinal study same subjects over a certain period of time.  From the study above, we can see that on-field-performance is the dependent variables. Since there is no way for the researchers to conduct and proof the psychological development, physical development ia the most suitable choice.

it should be c, women were allowed to vote in all states because federal law supersedes state law.

"states can make their own laws, as long as they don't contradict what the federal law states. the states do not have the authority to pass a law that negates a federal law." -google

the historians cited in the article all agree with one another about the cause of the civil war. despite coming from different backgrounds and cultures, the historians agree that slavery was the root cause of the civil war. the fact that all these historiansgenerally agree with one another makes their shared viewpoints more reliable and valid, especially because the historians have different backgrounds and all work for the well-respected institutions of howard university, clemson university, and the university of colorado.