A coherent paragraph requires a logical flow: introduction, elaboration, contrast, conclusion.
- Step 1: Identify introduction: Sentence 1 introduces social media as communication tools.
- Step 2: Find elaboration: Sentence 2 details their function (rapid sharing).
- Step 3: Identify contrast: Sentence 3 introduces a drawback (misinformation).
- Step 4: Find conclusion: Sentence 4 discusses regulation as a response.
- Step 5: Test order: 1-2-3-4 flows logically: introduction, benefit, drawback, response. Other orders (e.g., b starts with elaboration, d with conclusion) disrupt coherence.
Thus, the answer is a.