Which statement is true of an object in equilibrium?
a. the sum of all the horizontal lines are non0vertical
b. the sum of all the vertical lines are non0vertical
c. the sum of all forces on the object are zero
d. at least one of the forces on the object is zero

The sum of all forces on the object are zero

Explanation:

An object in equilibrium means it is balanced. In an equilibrium state, the total forces acting on it are balanced so net force is zero and then the system is said to be in equilibrium state.      

For example :  In attached figure, the forces acting in horizontal as well as vertical direction are equal and opposite. This gives the sum of forces acting on the object is zero. So, the system is in balanced state or in equilibrium state.

Hence, the correct option is (c).

the sun's light combined with the visible wavelenghts form what is called ultraviolet radiation, which are the long waves at the end of a visible light sprectrum.

hope it ,

bioteacher101