Placer mining involves to extract minerals.
a. removing the top layer of earth
b. tunneling under the earth
c. dredging sediments from the water bottom
d. none of the above

Which of the following statements best describes what is occurring in the land surrounding the sahara desert? a desertification is increasing, and the desert is expanding. b. fewer people are trying to farm in this semiarid region. c. the desert is shrinking with the increased use of irrigation. d. increased urbanization has resulted in decreased deforestation. select the best answer from the choices provided mark this and return save and exit next submit