Which of the following is the $CO_2$ acceptor in $C_4$ plants?

$C_4$ photosynthesis does not occur in

Even though a very few cells in a $C_{4}$ plant carry out the biosynthetic-Calvin pathway,yet they are highly productive. Can you discuss why?

Which of the following is shown by $CAM$ plants?

$A$ plant in your garden avoids photorespiratory losses,has improved water use efficiency,shows high rates of photosynthesis at high temperatures,and has improved efficiency of nitrogen utilisation. In which of the following physiological groups would you assign this plant?

Assertion: $C_4$ pathway of $CO_2$ fixation is found in some tropical plants.
Reason: In this pathway,$CO_2$ is fixed by $3C$ compound.