Step 1: Recall reforms timeline.
- 1909: Morley-Minto Reforms → separate electorates for Muslims.
- 1919: Montague-Chelmsford → expanded councils, dyarchy.
- 1927: Simon Commission → no Indian member, proposed reforms.
- Delhi Pact (Nehru Report, 1929) was different context.
Step 2: Apply to question.
Separate electorate for Muslims was first legally introduced in 1909 under Morley-Minto reforms.
Step 3: Conclusion.
Correct answer: (B) Morley-Minto Reforms.