Among the angles 30°, 36°, 45°, 50° one angle cannot be an exterior angle of a regular polygon. The angle is

Given options for exterior angles are 30°, 36°, 45°, 50°

we know that sum of all exterior angles in a regular polygon = 360°

now, individual exterior angle in regular polygon = $$\frac{360}{n}$$

where , n = number of sides in a polygon.

and hence we can say n should be a positive integer as number of sides can not be in fraction or negative .

Now start, checking given angles.

If exterior angle is 30° , then number of sides = $$\frac{360}{30}$$ = 12

If exterior angle is 36° , then number of sides = $$\frac{360}{36}$$ = 10

If exterior angle is 45° , then number of sides = $$\frac{360}{45}$$ = 8

If exterior angle is 50° , then number of sides = $$\frac{360}{50}$$ = $$\frac{36}{5}$$

as one can see that in last option of exterior angle 50°, number of sides is coming in fraction and hence this option is not valid.