Preliminary tests show that the drug known as Mephaline

This question follows a classical comparison form in CR. Very good question to practice.

The form is:
Before: .........(hidden statement)........
After event X: A better/worse than B

Conclusion 1: A and B must be different.
Conclusion 2: X did make A better/worse than B.

Assumption: Before: A and B were the SAME --OR-- had same starting points.
Confirm: Because: if A = B, after event X, A and B must increase/decrease the same level.

ANALYZE THE STIMULUS:
Fact: Mephaline is useful in treating people experiencing memory loss due to Alzheimer’s disease.
Fact: Mephaline did not appear to slow or reverse memory loss in people who experienced memory loss due to a brain injury.
Conclusion: There must be something qualitatively different about these two types of memory loss.

Which of the following most strengthens the conclusion in the argument above?

ANALYZE EACH ANSWER:

A. Mephaline works by acting on the medial temporal lobes of the brain.
Wrong. Out of scope.

B. The patients who took part in the tests had similar amounts of memory loss prior to the tests.
Correct. B confirms that the comparison is VALID. See theories above.

C. People with Alzheimer’s disease usually have impaired powers of speech.
Wrong. Out of scope.

D. Some of the people being tested were unaware that they were given a drug that was intended to reduce memory loss.
Wrong. Does not help. The fact that people know or not know they were given that drug does NOT affect those people's memory loss.

E. The average age of the people tested who had lost memory due to a brain injury was less than the average age of the people with Alzheimer’s disease.
Wrong. Weaken the argument. If those people are in different categories --> the comparison is INVALID.

Hope it helps.