Many Traits of Organisms, Such as Body Form and Color

Many traits of organisms, such as body form and color, are controlled by specific proteins, in turn controlled by the DNA genetic sequence of nucleotides. The genetic control of color, as in aphids, does not usually shift during the life of an organism. Researchers found that some specific aphid populations shift from an original red coloration to a green coloration. Genetics could be a factor, if some programmed shift could be identified. Environmental conditions of the living and nonliving habitat could be a factor. Either way, the chemistry and observed changes of pigment molecules in the aphids can be studied with the scientific method.
-The initial experiment of Koga and Fugatsu,in testing for any bacterial cause of aphid color change,involved all of these except

A) the specific amounts of red and green pigment molecules were initially measured as dependent variables.
B) a group of aphids infected with Rickettsiella bacteria was grown, then killed in order to produce an extract to test on red aphids.
C) a group of green aphids was grown, then killed in order to produce an extract to test on red aphids.
D) a group of red aphids was grown as a control group.
E) a group of red aphids was treated with the independent variable of Rickettsiella bacteria infection from green aphids.