Answer:
A. Quality of Life
Explanation:
Studying cause effect relationship between two variables :
Eg : Law of Demand - Price negatively effects quantity demanded , price is the independent variable effecting demand & quantity is the dependent variable being effected by price.
"Is the quality of life of nursing home residents affected by their functional ability or hearing acuity?" : Quality of life is being effected by hearing acuity, so it is the dependent (outcome) variable. Hearing acuity effects quality of life, so it is independent (causal) variable.