What might have made the original solar nebula begin to contract? ...

[APUS57]

What might have made the original solar nebula begin to contract?
 
  A) the Big Bang
  B) the formation of our arm of the Milky Way
  C) the shock wave from a nearby exploding star
  D) interstellar magnetism generated by pulsars
  E) the large amount of angular momentum in the nebula

Question 2

Based on its surface features, the most important event on Venus in the past billion years or so was
 
  A) a global repaving that erased essentially all the surface features that had existed earlier.
  B) the eruption of a giant volcano that formed one of Venus's continents.
  C) the impact of an unusually large asteroid that left a deep scar on one side of the planet.
  D) the onset of mantle convection, which caused Venus's lithosphere to split into plates like those on Earth.

[zacnyjessica]

Answer to Question 1

C

Answer to Question 2

A

[APUS57]

Excellent

[yeungji]

Gracias!