Which soil horizon is known as the zone of leaching?

Which soil horizon is known as the zone of leaching?
  a. A
  b. B
  c. C
  d. D
  e. O

Which chemical weathering reaction creates limestone caverns?
  a. solution
  b. oxidation and hydration
  c. desiccation
  d. hydrolysis
  e. elutriation

Which chemical weathering reaction transforms feldspar to clay?
  a. solution
  b. oxidation and hydration
  c. desiccation
  d. hydrolysis
  e. elutriation

Which chemical weathering reaction is basically the same as rusting?
  a. solution
  b. oxidation and hydration
  c. desiccation
  d. hydrolysis
  e. elutriation

Which of the following is NOT needed for plant growth?
  a. water
  b. air
  c. humus
  d. mineral matter
  e. All of these are needed.

What is a general term for fragmental rock at the Earth's surface?
  a. massive
  b. regolith
  c. xenolith
  d. basalt
  e. lithosphere