A student plans to conduct an experiment to determine how a change in the pH of water affects the populatio growth rate of algae. To ensure that her experimental data are validshe should - Highlight the correct answer A. hold the acidity of the water constant B. vary the temperature of the water used C. control the final algae population sizes D. use the same species in a trials

D). Use the same species in all trials.

Explanation:

The student must 'use the same species of algae' in all the trials conducted during the experiment in order to ensure the validity of experimental data. A variation in the species may affect the authenticity of the results because every species of organism require the different environmental conditions and has varied nature and adaptability according to the environment. Therefore in order to produce authentic and reliable outcomes,  the same species of algae should be used while observing how a variation in the pH level of water affects the growth rate of algae. Thus, option D is the correct answer.