Inability to control variables
Immune system becuase ur immune system helps get rid of sickneess
Answer: Option A.
Explanation:
Regression analysis is a statistical model for estimating the relationships among different variables.
Regression analysis helps to predict the value of the dependent variable which changes when any one of independent variables varies, while other independent variables remain fixed.
Generally Regression analysis are classified in linear and non-linear regression.
Hence, the correct option is A.