Without any force to change it, an object at rest stays at rest and an object in motion stays in motion. this demonstrates which of newton's laws?
question 3 options:

(a) newton's first law

(b) newton's second law

(c)newton's third law

Newton’s first law is stated by the given statement.

Option A

Explanation:

Newton’s first law states that an object will remain in its state at rest or motion until and unless an external unbalanced forces act on the object. If an object is motion with constant velocity then it will be moving until force acting in opposite direction of motion is applied on the object.

Similarly, an object when at rest could be moved only if unbalanced forces act on it. Also it should be known that the force needed to push an object should be greater than the frictional and inertial force acting on the object. So, the given statement describes the Newton’s first law of motion.

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.