Which of the following is an example of chemical weathering?
water breaking rocks
plant roots splitting rocks
acid dissolving limestone
wind breaking down rock

The chemicals in the water break down the rocks, so water breaking rocks is an example of chemical weathering :)
Also, acids are a form of chemical weathering, as the chemicals dissolve the limestone :) Hope this helped!!
The wind does not contain chemicals, nor is there a chemical process in the plant roots splitting the rocks.

The correct answer is b