Final answer:
Acid rain dissolving limestone is an example of chemical weathering because it chemically alters the rock, in contrast to the physical weathering processes described in the other options.
Step-by-step explanation:
The example of chemical weathering among the options given is d) Acid rain dissolving limestone. Chemical weathering involves the alteration of the chemical composition of rocks, often leading to the formation of new minerals. Acid rain is an example of this process, as it can react with minerals in rocks such as limestone, which is made primarily of calcium carbonate, resulting in the rock being dissolved and carried away by water.
On the other hand, options a), b), and c) describe mechanical or physical weathering processes. Erosion by wind, the freezing and thawing of water, and mechanical abrasion all involve physical forces that break down rocks into smaller pieces without altering their chemical composition.