Why are nails made of iron but not barium and phosphorus?

Due to the high strength of iron compared to that of barium and phosphorus the nails are made of iron.

Though iron oxidizes to form rust on reacting with water but it does not explode. Whereas barium reacts vigorously with water with evolution of hydrogen gas. Barium on reacting with other nonmetals results in the formation of poisonous substances. Phosphorus is never found in its pure form in nature and is combustible.

Hence, nails are made up of iron but barium and phosphorus are not suitable for making of nails.

Nails are made of iron but not barium and phosphorus

because actually barium and phosphorous are not strong as iron . Barium is very weak to be used in nail and phosphorous also can be break easily. But iron is stronger than these both and also its strength and weight are sufficient to be used in a nail so nails are made of iron but not barium and phosphorus.

answer; i believe that the correct answer is (a) potassium(k)