Answer: (c) seed type
Explanation:
An independent variable is the one which can be altered or manually manipulated in an experiment. The effect of such manipulation can be examined on the dependent variable of the experiment. The dependent variable cannot be manipulated in an experiment instead it is the outcome of the experiment.
The seed type is the correct answer because the seed type can vary and the effect of which can be examined on the seed germination process and rate of seed germination.