What do we mean by a mass extinction? A) the extinction of ...

[Lobcity]

What do we mean by a mass extinction?
 
  A) the extinction of large animals, such as dinosaurs
  B) the extinction of a large fraction of the world's plant and animal species in a relatively short period of time
  C) an extinction caused by the impact of an asteroid or comet
  D) the extinction of any species of plant or animal that has mass

Question 2

Nearly every aspect of astronomy is related in some way to the existence of gravity and to the motions which are responsible for a balance against gravity. How does this balance play a role for the miscellaneous objects of the solar system (i.e.
 
  , the asteroids and comets)? How can some aspect of this be used as a tool to determine masses in the solar system?

[wergv]

Answer to Question 1

B

Answer to Question 2

Asteroids and comets all orbit the Sun, some with highly eccentric orbits. Some comets have periods of millions of years. Gravity acting on and between comets and asteroids can be used to determine their masses and the masses of bodies affecting them.

[Lobcity]

TY

[wergv]

You're welcome