Select the option that can be used as a one-word substitute for the given group of words.
A group of vehicles travelling together, typically one accompanied by armed troops

* Convoy: A group of ships or vehicles traveling together, typically accompanied by armed troops, warships, or other vehicles for protection.
Fleet: A group of ships sailing together, engaged in the same activity, or under the same ownership.

Procession: A number of people or vehicles moving forward in an orderly, formal, or ceremonial manner.

Armada: A fleet of warships.

Therefore, 'Convoy' is the most appropriate one-word substitute.