The correct answer is: D. communication and storage.
A body area network (BAN) is a personal area network (PAN) that is worn on the body. BANs are used to connect medical devices, fitness trackers, and other wearable devices to the internet or to other devices. BANs can provide communication and storage for these devices.
Option A: Communication. BANs can be used to communicate with other devices. For example, a BAN can be used to connect a fitness tracker to a smartphone so that the fitness data can be stored on the smartphone.
Option B: Storage. BANs can be used to store data. For example, a BAN can be used to store medical data from a wearable device.
Option C: Network connectivity. BANs can be used to connect to the internet. For example, a BAN can be used to connect a fitness tracker to the internet so that the fitness data can be uploaded to a fitness tracking website.