It is difficult to draw clear conclusions from observational studies of diet and health because there are many confounding variables. a. True
b. False

i think  it is a

Explanation:

d is the answer hope this

lifetime activities are certain actions that are either required throughout your life or you choose to do them. for example, eating is considered a lifetime activity, drinking water or other beverages, keeping your body clean, taking medicine. those types of actions are considered lifetime activities.