The correct sequence of events is as follows: 4-3-1-2.

Option 1: 1-2-4-3

This sequence is incorrect because it starts with the Rowlatt Act (1) which was passed in 1919, while the Morley-Minto Reforms (3) were introduced earlier in 1909. The correct chronological order should be followed.

Option 2: 4-3-1-2

This sequence is correct. The Illbert Bill (4) was introduced in 1883, followed by the Morley-Minto Reforms (3) in 1909. The Rowlatt Act (1) was implemented in 1919, and finally, the Gandhi-Irwin Pact (2) was signed in 1931.

Option 3: 4-1-3-2

This sequence is incorrect because it places the Rowlatt Act (1) before the Illbert Bill (4). The correct order should have the Illbert Bill before the Rowlatt Act.

Option 4: 3-4-1-2

This sequence is incorrect because it places the Morley-Minto Reforms (3) before the Illbert Bill (4).