Consider the following planned experiment.
.
which variable is being tested in this experiment.

a. days of growth
b. temperature
c. antibiotic
d. type of culture medium

Cattle with brown fur and cattle with white fur will produce a reddish roan calf . when examined closely, the calf show about an even number of brown hairs and white hairs that give a reddish appearance when viewed from far away. the fact that both the brown fur allele and the white fur allele are expressed equally in the offspring is an example of