What must a driver do before leaving the cab?

Before leaving the cab, it is crucial for a driver to turn off the master control and take the key. This action is essential for safety and security purposes. Turning off the master control ensures that the vehicle or equipment cannot be inadvertently operated while unattended, which could lead to accidents or unauthorized use. Additionally, taking the key is a critical step to prevent theft or tampering with the vehicle. This combination of actions helps maintain control over the operation of the cab and ensures that any necessary safety protocols are followed before the driver exits the area.

The other options do not encompass all the safety procedures needed before leaving the cab. Some of these actions may not adequately secure the vehicle or ensure that all systems are safely shut down.