You are operating an IoT solution for a vineyard where a fleet of drones is used to monitor plants for possible infections. The drones, which have no direct network access, collect local weather data and they download them to docking stations at the end of their trips. The docking unit then transfers the data in batches to the central IoT Hub. Because of the low bandwidth, the docking stations can connect to the IoT network infrequently, for a few minutes only. You need to design a solution to get the data to the IoT Hub. 
Which device-to-cloud communication pattern should you use?

Answer options:

A.File upload
B.Device twin reported properties
C.Device-to-cloud messages
D.Direct methods

Correct Answer: A
Option A is CORRECT because when your devices send data in batches, for any reason, they should upload the data as files, using IoT Hub’s device facing endpoint dedicated for this type of operation.
Option B is incorrect because device twin reported properties are typically for short status data sent by the devices, e.g. battery charge level, connectivity mode etc. It is not suitable for large amounts of telemetry data.
Option C is incorrect because device-to-cloud messages are intended for devices with permanent and stable connection that they can use to stream telemetry data continuously.
Option D is incorrect because direct methods are a means of cloud-to-device communication. They are not suitable for the current scenario.
Reference: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-file-upload