Which of the following statements is incorrect? 

• A

  RuBisCO action requires ATP and NADPH.

• B

  RuBisCO is a bifunctional enzyme.

• C

  In ${\mathrm{C}}_4$ plants, the site of RuBisCO activity is mesophyll cell.

• D

  The substrate molecule for RuBisCO activity is a 5-carbon compound.