Which of the following statements is true of the Sahara Desert, the Arctic and sub-Arctic regions of North America?

• A.The areas inhabited by primitive hunters and traders
• B.These areas have the world's largest known deposits of crude oil
• C.population is found in isolated oases and along the river valley's
• D.The enviroment is very harsh for both man and animal
• E.The inhabitants belong to the oldest races in the world