The correct answer is D. Research shows that little actual schoolwork gets done in study periods and that midday breaks actually lower knowledge retention rates.
Explanation:
A thesis statement or thesis is a claim or position regarding some situation or subject, in this case, the thesis states removing "free" or "study" periods would make the school day more efficient. Additionally, for a thesis to be valid, it needs to be supported with evidence that can include examples, statistical information, findings from research studies or other reliable sources.
In this case, the best evidence is "Research shows that little actual schoolwork gets done in study periods and that midday breaks actually lower knowledge retention rates", because it explains "study" periods are not really necessary because the objective of these spaces is not usually achieved, and besides this study periods have a negative impact on knowledge retention rates, which suggest they affect negatively learning and thus, this suggest removing them would actually make the school day more effective which is what the thesis claims. Also, this shows the thesis is valid because other sources have found "study" periods are not completely beneficial.