Problem: Rob is competing in a cross country race. After running about a mile he reached a place with two signs, sign A and sign B. Sign A says that it's a quicksand. But sign B says that it's not a quicksand. He has to decide which way to go. In which way Rob would not sink, sign A or sign B?

A: sign B

Problem: Marco is sitting at the bottom of a mountain and painting a picture of it. Lauren, Marco's friend, is sitting about halfway up the mountain and painting a picture of the horizon. The two will compare paintings after they complete their drawings and then will switch places and repeat the task. These two friends do this a couple times a year, and they always enjoy seeing how the other person paints the same object. Is the air by Lauren more or less dense than the air by Marco?

A: less

Problem: Two biologists studied different living creatures. Matt studied protozoa, while his friend Greg studied nematodes and insects. Which friend studied more about predatory protozoa keeping bacterial populations in check?

A: Matt

Problem: John was studying the plate tectonics of earth. He specifically selected two locations, location A and location B. He noticed that location A had lot of plate tectonics activities, but location B didn't have much of that. He wondered how that would make difference in those locations' characteristics. Which location would have less volcanoes and earthquakes, location A or location B?

A:
location B