What is an essential characteristic of an object in equilibrium?
a. zero velocity
b. zero acceleration
c. zero momentum
d. zero energy

Zero acceleration is an essential characteristic of an object in equilibrium

Explanation:

Equilibrium is a condition or state of a system where the internal energy or motion of the object doesn't change with time. Also the force acting on the object will be zero. According to “Newton's second law of motion”, the acceleration of the object in equilibrium will be zero. There are two types of equilibrium namely static equilibrium and dynamic equilibrium. Static equilibrium is a state where the net force acting on object will be zero and the object will not be moving. In Dynamic Equilibrium, the force on the object will be zero and the object will be moving with an non zero constant velocity.

credit card number 4 is the right answer