What keeps some of the radiation from the sun in the atmosphere?

ozone

Explanation:

The ozone layer keeps the sun’s harmful radiation in the form of ultraviolet light out of the atmosphere thus protecting life on Earth. Harmful UV radiation causes skin cancer, cataracts and skin cancer. Ozone layer has been depleting because of the use of chlorofluoro carbon. But the reduced use of freons has helped the ozone to recovery itself quickly.

the answer is definitely c.

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.