I am pretty sure the answer is
D) Velocity
Glad I could help, and good luck!
AnonymousGiantsFan
Answer:
A. Type of soil
Explanation:
A control experiment is the one that is used to checkmate the real experiment.
In this case, the fourth jar that contains the mixture of all the types of the soil is considered as the control experiment.
In a nutshell, it should be generally understood here that the type of soil serves as the control for the experiment.
Lowercase b is the allele that goes in 3
