Which is the most reactive metal?

Correct answer: (b) Potassium

Explanation

In the reactivity series, metals are ranked by how readily they lose electrons; the topmost are most reactive.

The order here is Potassium (K) > Sodium (Na) > Calcium (Ca) > Iron (Fe), so potassium is the most reactive of the four.

Top metals are strong reducing agents that corrode and react vigorously, unlike less reactive iron.