An experiment comparing three drug typesA, B, and Cis performed. A group of subjects is divided into three groups by age: 2040, 4160, and 61+. The 20- to 40- yearolds receive drug A, the 41- to 60year olds receive drug B, and the 61+ group receives drug C. People administering the drugs know which subject is receiving which drug, but the subjects do not. Time to relief is measured for each subject. What are the obvious confounding variables in this experiment? 0 The age of the subjects and the drug type 0 The time to relief and the drug type ' O The subjects and the drug type 0 The person administering the drug and the drug type