Which of the following is correct for photosynthesis?

Sugar produced in photosynthesis is converted into starch in

Under conditions of constant illumination,the compensation period for a whole aquarium would be of infinite length when:

What percentage of usable radiant energy entering a reaction site of photosynthesis is converted to potential energy (in $\%$)?

Blackman demonstrated that increasing illumination increased the photosynthetic rate up to a point when $CO_2$ becomes limiting. If light was not limiting,temperature becomes limiting. Emerson found that maximum $CO_2$ fixation could be achieved with brief flashes of light. Mark the correct statement in the following:

Assertion : $C_4$ photosynthetic pathway is more efficient than the $C_3$ pathway.
Reason : Photorespiration is suppressed in $C_4$ plants.