What Evidence Suggests That Life Was Common on Earth Within

Multiple Choice

What evidence suggests that life was common on Earth within a billion years of its formation?

A) Life must have formed early in order to produce the variety of lifeforms seen today.
B) rocks older than 3.85 billion years with the carbon- 12 to carbon- 13 ratio typical of living organisms
C) 3) 5 billion year old rock structures formed by microbes called stromatolites
D) A and C
E) B and C