Cometary impacts with Jupiter A) are impossible to observe ...

[Sufayan.ah]

Cometary impacts with Jupiter
 
  A) are impossible to observe from Earth.
  B) are spectacular but do not teach us much.
  C) have been observed from Earth at least twice.
  D) are extremely rare.
  E) would not be catastrophic if they happened on Earth.

Question 2

What is the primary visible color of an emission nebula?
 
  A) blue due to ionized helium atoms
  B) red due to the H line of hydrogen
  C) black, because of dust
  D) blue from the scattering of light off the tiny molecules
  E) red because of reddening by dust

[vkodali]

Answer to Question 1

C

Answer to Question 2

B