LONGMAN TOEFL--- R/C

 

Example II

 

The passage:

 

Nitrogen fixation is a process by which nitrogen is continuously fed into biological circulation. In this process, certain algae and bacteria convert nitrogen into ammonia (NH₃). This newly created ammonia is then for the most part absorbed by plants.

 

The opposite process of denitrification returns nitrogen to the air. During the process of denitrification, bacteria cause some of the nitrates from the soil to convert into gaseous nitrogen or nitrous oxide (N₂0). In this gaseous form the nitrogen returns to the atmosphere.

 

The question:

 

Which of the following would be the best title for this passage?

 

(A) The Process of Nitrogen Fixation

(B) Two Nitrogen Processes

(C) The Return of Nitrogen to the Air

(D) The Effect of Nitrogen on Plant Life