Problem: The ecologist moved from Aspen, where there was no air pollution, to Seattle which experienced a lot of air pollution. He started studying the weather there as well. Which city had more conditions for developing acid rain?

A: Seattle

Problem: Two friends met after 20 years. Tom had been smoking tobacco all these years and had some health problems related to that, while Randy quit smoking 25 years ago. Which friend was at a lower risk for developing cancer?

A: Randy

Problem: Town A disposed of the biomedical waste from their hospital conventionally in a regular dump site for 10 years because it was more convenient, while town B took them to an ecological site where they wouldn't affect ground water and spread disease. Which town is experiencing fewer mosquitoes?

A: town B

Problem: Jacob recently contracted the HIV virus and is going to his first support meeting. While there, he meets Dan and strikes up a conversation with him. Dan says that he has had HIV for over a decade at this point and has learned ways to live with it. He is able to give Jacob some good advice on how to handle things and Jacob is very grateful to have someone to talk with. Is Dan's immune system weaker or stronger than Jacob's?

A:
weaker