(A) Alliances
(B) ** Convoy
(C) Contour
(D) Tactical formation
EXPLANATIONS BELOW
Concept note-1: -countable noun [oft in NOUN] A convoy is a group of vehicles or ships travelling together.
Concept note-2: -convoy, vessels sailing under the protection of an armed escort. Originally, convoys of merchant ships were formed as a protection against pirates.
Concept note-3: -A march column consists of two to five serials. A serial consists of elements of a march column (convoy) moving from one area over the same route at the same time. All the elements move to the same area and are grouped under a serial commander. The serial commander is directly responsible to the convoy commander.