The diameter of a wheel is 84 cm.

(c) 300

Let d cm be the diameter of the wheel.
We know:

Circumference of the whee $=\pi \times d$

$=\left(\frac{22}{7} \times 84\right) \mathrm{cm}$

$=264 \mathrm{~cm}$

Now,

Number of revolutions to cover $792 \mathrm{~m}=\left(\frac{792 \times 1000}{264}\right)$

$=300$