Explanation

(d)
According to collision theory,
1. The reaction rate depends on collision frequency and effective collisions. For a molecule to have effective collision it should fulfill two conditions; proper orientation and sufficient energy.
2. The collision rate $i.e$., the number of collisions taking place in unit volume is also termed as collision frequency ($Z$) and is given by
$z = \frac{\pi n^{2}\sigma^{2}u_{av}}{\sqrt{2}}$
3. Greater the temperature, greater will be the collision rate.