Who proposed the theory of photosynthesis in guard cells?

The two pigment system theory of photosynthesis was proposed by

Explain the information about the discovery of $C_3$ and $C_4$ pathways.

$ATP$ is produced during:

All the energy for living organisms comes as radiation in the form of......from the sun and is captured by.......

Which of the following statements with regard to photosynthesis is/are correct?
$I$. In $C_{4}$-plants,the primary $CO_{2}$ acceptor is $PEP$.
$II$. In the photosynthetic process,$PS-II$ absorbs energy at or just below $680 \;nm$.
$III$. The pigment that is present in the Pigment System-$I$ is $P680$.