Statement I: Petroleum is a mixture of many different hydrocarbons of different densities. Statement II: The grade of petroleum depends mainly on the relative proportion of the different hydrocarbons.

• A

  Both the Statements are individually true and Statement II is the correct explanation of Statement I.
• Correct answer
  B

  Both the Statements are individually true but Statement II is not the correct explanation of Statement I.
• C

  Statement I is true but Statement II is false.
• D

  Statement I is false but Statement II is true.

Hence, the correct answer is option: 'B'.