Why may an initial measurement be necessary in an experiment?

Correct answer: To determine the actual change

The correct answer is option A: an initial measurement helps determine the actual change. The first measurement is called the baseline or starting value. After the experiment or treatment, a final measurement is taken. The change is found by subtracting the initial value from the final value: change = final measurement − initial measurement. For example, if a plant is 10 cm initially and 14 cm later, its increase is 14−10=4 cm. Without the starting value, we know only the final condition, not how much it changed. Option B is wrong because a sound experiment does not decide its result in advance; the evidence should determine the conclusion. Option C is wrong because an initial measurement does not remove a control group; controls help provide a comparison. Option D is wrong because the baseline makes the investigation clearer and does not hide the hypothesis. The exam cue is to compare before and after, not only the final reading.