Since the origin and diversification of life on Earth, there have been five episodes of mass extinction of species. How is the sixth extinction, which is in progress, different from the previous episodes?

• A
  $(1)$ The current species extinction rates are far lower than those in previous episodes.
• B
  $(2)$ The present species extinction rates are $100$ to $1000$ times faster than in the pre-human times.
• C
  $(3)$ The present net species extinction rate is zero.
• D
  $(4)$ The current species extinction rate is nearly $10$ times faster than in previous episodes.