What is the center of a hurricane called?

cloud
cyclone
eye
typhoon

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because

Which structure in the cardiovascular system connect arteries to veins?

What would most likely happen to a unicellular organism if it was exposed to a hypotonic solution for an extended period of time?