Yoghurt Production Sequence Steps:

• Pasteurize milk (4) to eliminate pathogens and ensure safety.
• Add bacterial culture (3) to the warm pasteurized milk for fermentation.
• Incubate at 40-45°C for 3 hours (2) to allow bacteria to convert lactose to lactic acid, thickening the milk.
• Rapidly cool the mixture (1) to stop fermentation and set the yoghurt texture.

Why D is correct:

• D follows the standard yoghurt process: pasteurization sterilizes milk before inoculation (3), incubation (2) enables bacterial activity, and cooling (1) preserves the product, per food microbiology principles.

Why the others are wrong:

• A: Begins with cooling (1), but unpasteurized milk risks contamination.
• B: Incubates (2) before pasteurization (4), allowing unwanted microbes to grow.
• C: Adds bacteria (3) before pasteurization (4), killing the culture via heat.

Final answer: D