The best experimental design: a. alters only one condition between the controls

The correct answer is option d. "includes a large sample size and a control, and alters only one condition between the controls and the experimental condition".

Explanation:

The correct answer for this question is missing, which is option d. "includes a large sample size and a control, and alters only one condition between the controls and the experimental condition". The best experimental design includes all the options proposed: it includes a large sample size to ensure that the data is statistically relevant; a control to verify that the results are valid and are not obtained from other untested conditions; and it alters only one condition at the time to ensure the existence of the relation between condition and results.

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 The correct location is inside the ovaries!