What happens when you climb higher? a You get less oxygen. b You get more oxygen.
2 Where are the three groups of people the scientists studied? a Tibet, Peru and Ethiopia. b Europe, Australia and North America.
3 What did hunters use to make clothes? a Animal meat. b Animal skin.
4 How can the people live at high altitudes? a Because they breathe faster, have thicker blood or maybe have different genes. b Because they wear warm clothes.
