The $CO_2$ concentration at which $C_4$ plants show saturation is about (in $ppm$)

Which of the following statements is false regarding Kranz anatomy?

Under what conditions are $C_4$ plants superior to $C_3$ plants?

Choose the incorrect statement regarding bundle sheath cells.

The chloroplasts present in the bundle sheath cells of $C_4$ plants are . . . . . . .

Enzyme $RuBisCO$ acts as both a carboxylase and an oxygenase. Why is it said that $RuBisCO$ in $C_4$ plants performs more carboxylation?