Questions 13 to 15 are based on the passage you have just heard.
13
A.They provide goods and services to over half of the world's population.
B.They are important areas for summer sports.
C.They cover about one-tenth of the world's land surface area.
D.They provide water for millions of people in the world.
14
A.There is often very little economic activity in mountain areas.
B.Mountain environments are not supervised well all the time.
C.Children who live in mountain areas can't afford to go to schools.
D.There are less and less plants and animals.
15
A.It has strengthened its supervision in mountain areas.
B.It has sent some experts to mountain areas to do some researches.
C.It has planned many activities for next year.
D.It has carried out some rules and regulations on cutting down trees.