Sentence 3 is off-topic because it talks about gardeners deciding on pesticides; that information isn't necessary in a paragraph about how gardening is therapeutic. The answer is B, sentence 3.
The answer is b. Sentence three talks of choosing pesticides for your garden. It has nothing to do with the benefits gardening brings upon a person. It mentions nothing of stress relief or other health benefits. All of the other sentences describe how gardening can benefit a person. Sentence three does not describe how gardening can benefit a person and therefore it is the off topic sentence.
