If an object is to rest on an incline without slipping, then friction must equal the component of the weight of the object parallel to the incline. this requires greater and greater friction for steeper slopes. show that the maximum angle of an incline above the horizontal for which an object will not slide down is θ.

Explanation:

As we know that if the object is placed on the inclined plane then the force of friction on the object is counterbalanced by the component of the weight of the object along the inclined plane.

So we can say

now if we increase the inclination of the plane then the component of the weight weight along the inclined plane will increase and hence the friction force will also increase.

As we know that the limiting value or the maximum value of friction force at the static condition is given by

so we have

so we will have

so now we have

so maximum possible angle of the inclined plane is

electrical power

real, smaller and upside-down.   so the answer should be b.