Explanation:

All of the above codes are correct.

• Firstly, Drones are employed in agriculture for a variety of purposes such as estimating the planted area and likely production, assessing crop damage by pests and diseases, and digitising land records, apart from their most common use for spraying pesticides and plant nutrients.
• Secondly, The use of drones in the farm sector is unlikely to remain confined to a few broad areas, such as spraying, surveying, mapping, and surveillance.
• Thirdly, Specially designed sensors equipped with artificial intelligence tools can enable drones to distinguish between healthy and diseased or pest-infested plants for better targeting of pesticides and other plant-protection chemicals.
• Fourthly, large drones can be used to transport farm produce, especially perishable items like vegetables, fruit, meat, and fish, to markets directly from farms in the least possible time and with minimum damage to the stuff.

Hence option 4th is correct.