The correct answer is: D. None of these
The guard shall ask the LP to start the train on telephone.
Walkie-talkie is a handheld two-way radio. It is a short-range communication device that uses radio waves to transmit and receive voice signals. Walkie-talkies are typically used for personal communication, such as between parents and children, or between friends who are hiking or camping. They can also be used for business purposes, such as by security guards or construction workers.
VHF stands for Very High Frequency. VHF radio waves are used for a variety of purposes, including television broadcasting, two-way radio communication, and air traffic control. VHF radio waves have a longer range than walkie-talkie signals, but they are not as good at penetrating buildings or other obstacles.
Telephone is a communication device that allows two or more people to talk to each other over a long distance. Telephones work by converting sound waves into electrical signals, which are then transmitted over wires or through the air. Telephones are one of the most common forms of communication in the world.
In the case of a train, the guard and the loco pilot need to be able to communicate with each other at all times, especially when the train is moving. Walkie-talkies and VHF radios are not reliable enough for this purpose, as they can be easily blocked by buildings or other obstacles. Telephone is the most reliable way for the guard and the loco pilot to communicate with each other, as it is not affected by obstacles.