Why are landfills filling up?
a) more people are producing more garbage?
b) many people don't recycle their garbage?
c) metal containers cannot be reused?

the geysers in yellowstone part suggests that:
a) there was a major eruption 1,000 years ago
b) the area is still a hot spot
c) no more explosions will occur in the future
d) a plate in that area is moving apart