Answer:
The correct answer will be option-C.
Explanation:
A scientific experimental design includes three types of the variables or parameters: independent variable (a variable which can be manipulated), dependent variable (which is to be studied ) and the constant variable (variable kept constant throughout the experiment).
In the given question, the dependent variable is the germination of seeds, the independent variable is pH and the constant should be temperature, number and species of the seeds.
Since the temperature and species of seed are different in every Petri-plates and is not being controlled or kept constant, therefore, Option-C is the correct answer.
