the 3 studies that can be used to determine associations between variables are case report, cohort studies, and systematic review.

answer: all of the above

a. apply ice to the affected area.

b. administer tylenol (acetaminophen).

c. put a gate across the stairs.

d. apply knee and elbow protectors.

...~ Activity theory predicts that older people will do different activities than younger people, with more time budgeted for leisure. The relationship between age and time spent doing these leisure activities with others, under activity theory, is hypothesized to be positive. ~...

I hope I helped!~

-Koko uwu