From where can parking brakes be applied?

Parking brakes are essential safety features that allow the operator to secure a vehicle when it is stationary. The correct answer highlights the flexibility and functionality of parking brake systems within engineering vehicles or train operations. Applying the parking brake from any engineer's cab with an active master controller ensures that the engineer or operator can secure the vehicle regardless of their position within the apparatus.

This capability is particularly important in scenarios where immediate action is necessary, enabling quick response times to prevent accidents or unintended movement. The design of safety systems like parking brakes usually prioritizes accessibility from multiple operational points to enhance safety protocols and operational efficiency.

Other choices imply limitations that do not reflect the advanced operational standards found in modern vehicles and systems where safety and responsiveness are critical. For instance, fixing application points to ground level or specific cabs would restrict operational flexibility and safety, which is contrary to established engineering practices.