What evidence do scientists have that earth has been hit by large objects, like asteroids, in the past? check all that apply.

I have attached a screenshot of the question and its options.

layer of burned organic matter
change in average global temperature
mass extinctions

Explanation:
Asteroids are external rocks/objects that hit the surface of the earth.
Let's check the options:
1- layer of volcanic ash: This option is rejected as volcanoes are caused as a result of the internal heat and combustion in the layers of the earth. Therefore, volcanoes are independent of external bodies as asteroids.

2- layer of burned organic matter: This option is accepted. When bodies , as asteroids, hit the earth, their clash with the earth's surface usually lead to burns and/or fires leading to layers of burnt organic matter that is found on the surface of the earth and its underlying layers.

3- change in average global temperature: This option is accepted as these bodies usually have different temperatures than that of the earth's climate. Therefore, when they penetrate the earth's atmosphere, they can lead to a change in the global temperature.

4- mass extinctions: This option is accepted as the collision of these bodies with the earth's surface can lead to destruction of creatures/objects which may lead to mass extinctions.

5- earthquake activity: This option is rejected as earthquakes are formed as a result of the motion of plates within the layer's of the earth and not as a result of external bodies.

Hope this helps :) 

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).