(A) ** convoy
(B) flotilla
(C) regiment
(D) zeppelin
EXPLANATIONS BELOW
Concept note-1: -A convoy is a group of vehicles or ships travelling together. The army vehicles travelled in convoy.
Concept note-2: -A convoy may be as small as a six-vehicle march unit or as large as a 300-vehicle column. A convoy commander can better control a convoy if it is broken into smaller, more manageable groups. Whenever possible, convoys are grouped along organizational lines, such as platoon, company, and battalion.
Concept note-3: -us. /ˈkɑn·vɔɪ/ a group of ships or vehicles that travel together, esp. for protection: a convoy of supply ships.
Concept note-4: -A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection.
Concept note-5: -convoy, vessels sailing under the protection of an armed escort. Originally, convoys of merchant ships were formed as a protection against pirates.