(A) ** bottom of a vessel
(B) lower part of the leg
(C) salute
(D) a speech
EXPLANATIONS BELOW
Concept note-1: -keel, in shipbuilding, the main structural member and backbone of a ship or boat, running longitudinally along the centre of the bottom of the hull from stem to stern. It may be made of timber, metal, or other strong, stiff material.
Concept note-2: -The keel is basically a flat blade sticking down into the water from a sailboat’s bottom. It has two functions: it prevents the boat from being blown sideways by the wind, and it holds the ballast that keeps the boat right-side up.
Concept note-3: -The keel is the bottom-most longitudinal structural element on a vessel.
Concept note-4: -The keel is often a structural beam that runs in the middle of the boat from bow to stern. The purpose of the keel is to help give the boat greater stability and control while moving forward. Without the keel, a boat might slip or skim on the water which is often common in vessels with an entirely flat bottom.
Concept note-5: -The keel of a ship is similar to the spinal cord of humans. As the spine functions to keep our backbone upright by linking and supporting our body, the keel is the primary structural member and backbone of the vessel which runs along the centreline of the bottom plate around which the hull of the ship is built.