The _____ is a geologically brief period about 540 million years ...

[jon_i]

The _____ is a geologically brief period about 540 million years ago during which fossil evidence indicates Earth life became complex and diverse.
 
  A) Cambrian explosion
  B) Paleozoic era
  C) Renaissance
  D) Ordovician

Question 2

Which of the following does N represent in the Drake equation, Nc = N  fp  nHZ  fL  fI  fs?
 
  A) The average number of planets in a solar system
  B) The fraction of stars that have planets
  C) The number of stars in our galaxy
  D) The fraction of suitable planets on which life begins

[jomama]

Answer to Question 1

A

Answer to Question 2

C

[jon_i]

TYSM

[Sarahjh]

Thanks for the timely response, appreciate it