An article in the San Luis Obispo Tribunet described an experiment designed to Investigate the effect of creatine supplements on the development of m the researchers "looked at 19 men, all about 25 years of age and similar In weight, lean body mass, and capacity to lift weights. Ten were given creatir followed by 5 grams a day for the rest of the study. The rest were given a fake preparation. No one was told what he was getting. All the men worked trainer. The response variable measured was gain in fat-free mass (In percent)." (a) What extraneous variables are Identified In the given statement. (Select all that apply.) age Oheight O hair style capacity to lift weights lean body mass weight eye color gender X