Which group among the following contains the most commonly encountered combustible metals?

The group that contains the most commonly encountered combustible metals is that which includes magnesium, sodium, potassium, and calcium. These metals are known as alkali and alkaline earth metals, and they are characterized by their reactivity and ability to ignite easily under certain conditions.

Magnesium, for instance, is frequently used in manufacturing and is well-known for its flammability, especially when in fine forms like shavings or dust. Sodium and potassium are highly reactive metals that can ignite spontaneously when exposed to moisture or air, making them significant in both chemical and fire hazards. Calcium, while not as reactive as sodium and potassium, can still burn when heated.

Conversely, the other groups listed consist of metals that are less likely to spontaneously ignite or present significant combustible hazards under normal handling or use conditions. Iron, copper, aluminum, and nickel, while they can burn under extreme conditions, are not categorized as highly combustible metals. Lead, mercury, tin, and zinc are metals that do not have the same reactive properties and are generally much more stable. Steel, brass, silver, and gold are also less reactive, with steel being an alloy that primarily does not exhibit combustion under typical circumstances.

Thus, the most commonly encountered combustible metals, characterized by their