When we are using external sensors in a mobile computing system model, why is it necessary to send data in the open?

Group of answer choices

The sensors use Bluetooth, which only sends data in the open without encryption.

Encryption is time$-$consuming and resource$-$hungry.

There is no established security protocol to secure data communication between sensors and smartphones.

The sensors use Bluetooth, which uses a unique key to pair the sensor and smartphone, so the communication is already secure and does not require new encryption schemes.