The rate of cratering: A) has remained constant over the last ...

[ap345]

The rate of cratering:
 
  A) has remained constant over the last 4.6 billion years.
  B) has recently increased with more collisions in the asteroid belt.
  C) fluctuates over time, with massive bodies occasionally coming in from the Oort Cloud.
  D) shows that large asteroid impacts are more common now than in the past.
  E) shows that most interplanetary debris was swept up soon after the formation of the solar system.

Question 2

While our Milky Way's black hole is not massive enough to have once been quasar, it must have passed through its Seyfert phase by 3.5 billion years ago. Explain how we know this.
 
  What will be an ideal response?

[stanleka1]

Answer to Question 1

E

Answer to Question 2

We are here. Life on Earth would have been destroyed by the violent activity of an active nucleus only 30,000 light years away, in the core of our own galaxy, yet the fossil record tells us life has persisted on Earth uninterrupted for at least 3.5 billion years.

[ap345]

Both answers were spot on, thank you once again

[stanleka1]

Great! Please up vote