Can someone please help me answer these 2 bio questions?

Imagine you have three samples: sample 1 receives no treatment, sample 2 receives a drug that accelerates cellular division, and sample 3 receives a drug kills cells. Using the MTT assay, which sample would have the intermediate OD value? Select one: a. Sample 1 b. Sample 2 c. Sample 3 d. Both samples 1 and 3 e. There is not enough information to answer this question. The purpose of the positive and negative controls in an experiment is to Select one: a. Assess if the experiment system(assay) is working as expected b. Test the hypothesis c. Eliminate confounding variables d. Measuring the dependent variable e. Measure the independent variable