The reaction 2kclo3 (s) -> 2kcl (s) + 3o2 (g) is a

(C) Decomposition reaction

Explanation:

A decomposition reaction is a chemical reaction in which a single compound breaks down into two or more compounds or elements.

in this example

Potassium chlorate (KClO₃) decomposed to two smaller compounds KCl and O₂ gas.

So, the right choice is (C) Decomposition reaction

c. 4.54 x 10–12 j happens to be correct