The correct answer is D. 14 m/s.
The maximum velocity for the overturn of a car moving on a circular track of radius 100 m is given by the following formula:
$$v_c = \sqrt{\frac{rg}{\mu}}$$
where $r$ is the radius of the track, $g$ is the acceleration due to gravity, and $\mu$ is the coefficient of friction between the road and tyre.
In this case, $r = 100$ m, $g = 9.8 \frac{m}{s^2}$, and $\mu = 0.2$. Substituting these values into the formula, we get:
$$v_c = \sqrt{\frac{(100 \text{ m})(9.8 \frac{m}{s^2})}{0.2}} = 14 \text{ m/s}$$
Option A is incorrect because it is too small. Option B is incorrect because it is too large. Option C is incorrect because it is a unit of speed, not a velocity.