An area with a high population density has

a. few people living in a large area

b. a large population in a large area

c. a large area of arable land

d. many people living in a small area

Which of the layers of the earth has the following three characteristics? i. it is a solid outer layer. ii. it is between 3 and 30 miles thick. iii. it is separated into plates. a. the outer core b. the inner core c. the mantle d. the crust