Environmental Science & Technology (Oct. 1993) published an article that investigated the variables that affect the sorption of organic vapors on clay minerals. The independent variables and levels considered in the study are listed here. Identify the type (quantitative or qualitative) of each.

a. Temperature (50°F, 60°F, 75°F, 90°F)

b. Relative humidity (30%, 50%, 70%)

c. Organic compound (benzene, toluene, chloroform, methanol, anisole)