Internal energy is defined as.

a. the total kinetic energy of all the system component.

b. the total potential energy of all the system components.

c. the total of the potential and kinetic energies of all the system components.

d. the total potential energy minus the total kinetic energy of all the system components.

e. the total kinetic energy minus the total potential energy of all the system components.

Internal energy is defined as the total kinetic energy of all the system component.

Explanation:

Internal energy is defined as the sum of all the energies present within the molecules of an object due to their disordered and random motion.

Also we can say that, all the kinetic energies present within the molecules of an object are internal energy.

As kinetic energy is the energy obtained by the molecules of an object due to its motion.

Thus, we can conclude that internal energy is defined as the total kinetic energy of all the system component.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.