OG详解-OG7 数学2 Q1

Choice A is correct. It’s given that a total of 165 people contributed to a charity event as either a donor or a volunteer. It’s also given that 130 people contributed as a donor. It follows that 165-130, or 35, people contributed as a volunteer.
Choice B is incorrect. This is the number of people who contributed as a donor, not a volunteer. Choice C is incorrect. This is the total number of people who contributed as either a donor or a volunteer, not the number of people who contributed as a volunteer. Choice D is incorrect and may result from conceptual or calculation errors.