Judge the following sentence according to the criteria given below: Soluble nitrogen compounds in ...

Judge the following sentence according to the criteria given below: Soluble nitrogen compounds in the ocean completely recycled up to 10 times per year BECAUSE nitrogen compounds are among the most studied in chemical oceanography.
 
  A) The assertion and the reason are both correct, and the reason is valid.
  B) The assertion and the reason are both correct, but the reason is invalid.
  C) The assertion is correct, but the reason is incorrect.
  D) The assertion is incorrect, but the reason is correct.
  E) Both the assertion and the reason are incorrect.