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).

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.

b is the answer and if you need further with anything message me