OG详解-OG8 文法 Q29

Choice B is the best answer. The sentence effectively explains an advantage of infilling: it’s less invasive than using a power grinder. 
Choice A is incorrect. The sentence identifies a disadvantage of power grinding; it doesn’t explain an advantage of infilling. Choice C is incorrect. The sentence identifies the two techniques park rangers use; it doesn’t explain an advantage of infilling. Choice D is incorrect. The sentence indicates that power grinding and infilling are different in one aspect; it fails to explain an advantage of infilling.