Which of the following is an example of a chemical reaction?

مندرجہ ذیل میں سے کون سی کیمیائی رد عمل کی مثال ہے؟

Water freezing into ice

Sand settling to the bottom of a pool

Leaves changing colors in the fall

A rock rolling down a hill

Leaves changing colors in the fall is an example of a chemical reaction.
During this process, the production of chlorophyll (the green pigment) slows down, and the production of other pigments.
Like carotenoids and anthocyanins increases, causing the leaves to change color.