Final answer:
The best-suited fire extinguisher for a smoking metallic waste on the verge of igniting would be a Class D fire extinguisher.
Step-by-step explanation:
The best-suited fire extinguisher for a situation where metallic waste is smoking and on the verge of igniting would be a Class D fire extinguisher.
Class D fire extinguishers are specifically designed to extinguish fires involving combustible metals, such as magnesium, sodium, potassium, and titanium. These extinguishers use a dry powder agent, such as sodium chloride or graphite, to smother the fire and prevent its spread.
It is important to note that Class D fire extinguishers should only be used by individuals who have received proper training in handling them, as they can react violently if used on the wrong type of fire.