The correct statement(s) pertaining to the following reactions is(are):

• Correct answer
  A

  The reaction in which the product has the same number of carbon atom as that in the reactant is II.
• Correct answer
  B

  The reactions in which optically active reactant gives optically active product are III and IV.
• C

  The reaction in which one of the products has one carbon atom less than the reactant is I.
• Correct answer
  D

  The reaction in which the product has one carbon atom more than the reactant is III.

Hence, the correct answer is options: 'A', 'B', 'D'.