$A-$ The $C_3$ and $C_4$ plants respond differently to $CO_2$ concentrations.
$R -$ The concentration of $CO_2$ in the atmosphere is between $0.03$ and $0.04$ percent. An increase in concentration up to $0.05$ percent can cause an increase in $CO_2$ fixation rates.

Identify the incorrect sentences:
$(I)$ Humidity in the atmosphere is relatively higher in areas where light becomes a limiting factor for plants.
$(II)$ An increase in light intensity beyond a certain point causes the breakdown of chlorophyll,leading to a decrease in the rate of photosynthesis.
$(III)$ $C_4$ plants respond to higher temperatures and show higher rates of photosynthesis,while $C_3$ plants have a much lower temperature optimum.

Compensation point is

State the saturation point of $C_3$ and $C_4$ plants with respect to the concentration of $CO_2$.

Write the effect of concentration of $CO_2$ on $C_3$ and $C_4$ plants.

For which of the following plants is light rarely a limiting factor?