Chemosynthesis and photosynthesis are alike in that both

If $CO_2$ is released during respiration,why does the concentration of $CO_2$ in the atmosphere remain relatively constant?

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:

How do plants obtain their nutrition?

How many plants in the given list can produce $3C$ compound after carboxylation of $\text{RuBP}$? Pineapple,Maize,Rice,Mustard,Sorghum,Opuntia,Tomato,Wheat.

$I.$ Initial $CO_{2}$ acceptor
$II.$ Extent of photorespiration
$III.$ Enzyme catalyzing reaction that fixes $CO_{2}$
$IV.$ Presence of Calvin cycle
$V.$ Leaf anatomy
Which one does not differ in a $C_{3}$ and $C_{4}$ plant?