The idea of base level refers to A) an evolutionary cycle of ...

[kamilo84]

The idea of base level refers to
 
  A) an evolutionary cycle of landscape development from fluvial action.
  B) the amount of discharge in a particular reach of a stream.
  C) a level below which a stream cannot erode its valley.
  D) the stream gradient.
  E) the average height of a stream channel.

Question 2

The residence time of carbon dioxide (CO2 ) is
 
  A) 50 to 200 years.
  B) approximately 90 days.
  C) 45 days.
  D) 50,000 years.
  E) 12 years.

[jaygar71]

Answer to Question 1

C

Answer to Question 2

A