The concept being tested here is Mixture Problems — specifically, the weighted average boundary rule. The "which of the following MAY be true" format is deliberate: it punishes students who assume any value between 40% and 60% is automatically valid.
Step 1 — Find the alcohol percentage in each solution.
Solution A: ratio 2:3 → alcohol = 2/(2+3) = 2/5 = 40%
Solution B: ratio 3:2 → alcohol = 3/(3+2) = 3/5 = 60%
Step 2 — Apply the weighted average principle.
When two solutions are mixed, the resultant percentage is a weighted average of the two individual percentages, weighted by volume. If A has volume a and B has volume b (both > 0):
Resultant % = (0.4a + 0.6b) / (a + b)
This value is strictly between 40% and 60%. It approaches 40% only as b → 0, and approaches 60% only as a → 0. But the problem says A and B are mixed — meaning both are present in positive, non-zero quantities.
Step 3 — Evaluate each option.
I. 40% → Only if b = 0 (no B used). Not a genuine mix. ✗
II. 50% → Achieved when a = b (equal volumes). Valid. ✓
III. 60% → Only if a = 0 (no A used). Not a genuine mix. ✗
Answer: B (II only)
Common trap: Students see 40% and 60% as the endpoints of the possible range and include them. The word "mixed" is doing critical work here — it rules out using just one solution, which means the exact boundary values are unreachable. aditya1818 raised this edge case correctly; the issue is that "mixed" on the GMAT means a genuine combination of both, not a theoretical limit as one volume approaches zero.
Takeaway: On mixture "may be" questions, the resultant percentage lives in the open interval (lower%, upper%) — the endpoints are only reachable by using a single solution, which by definition isn't a mixture.