Drones, due to their ability to reach locations that might otherwise be dangerous or inaccessible for humans, have a wide range of applications.
Option 1 suggests drones can be used for spraying pesticides on a crop field and inspecting the craters of active volcanoes. This is correct as there are already drones specially designed for agricultural usage which can effectively spray crops. Likewise, drones can be used to safely approach and observe active volcanoes.
Option 2 suggests drones can be used for inspecting the craters of active volcanoes and collecting breath samples from spouting whales for DNA analysis. This is correct because, in addition to the reasons mentioned above, drones also have the ability to fly low over water surfaces and can be equipped to collect samples.
Option 3 suggests drones can be used for spraying pesticides on a crop field and collecting breath samples from spouting whales. This is also correct for reasons stated earlier.
Option 4, the right answer, correctly implies that with current technology, drones can perform all three activities: spraying pesticides on a crop field, inspecting the craters of active volcanoes, and collecting breath samples from spouting whales for DNA analysis.