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.
We reject the options a) and b) since the question says that the data supports "equally" both cases - so we have no basis for making a choice either way.
Further, in science the decisions are reached based on facts, not voting, so we also reject the answer D .
We are left with the answer C and this is also the best practice in science - when unsure, leave it as a hypothesis.
It takes approximately 4 days in Coon years.
