The correct statement is

• A
  $1 \text{ mole}$ each of benzene and hydrogen when reacted gives $1/3 \text{ mole}$ of cyclohexane and $2/3 \text{ mole}$ unreacted hydrogen.
• B
  It is easier to hydrogenate benzene when compared to cyclohexene.
• C
  Cyclohexadiene and cyclohexene cannot be isolated with ease during controlled hydrogenation of benzene.
• D
  Hydrogenation of benzene to cyclohexane is an endothermic process.