Answer:
D. Using the new fertilizer produces bigger tomatoes than using the
old fertilizer.
Explanation:
This hypothesis is best to test for the effect of the new pesticide on the tomato plant.
A pesticide is a chemical formulation used to kill pests of farm crops.
Pests prevent the healthy and proper growth of plants thereby resulting in poor yield on the farm.
For the farmer to ascertain the effect of the pesticide on his farm crop, he must compare the yield of his produce. Some tomatoes might grow well but would not bear good fruit. If the farmer focuses on the fruit produced, he would have derived a good hypothesis in his experiment.
I hope this helps :)