What is the Cambrian explosion?
A. An evolutionary period that began 540 million years ago
B. A period when a large number of new animals appeared
C. Neither a nor b
D. Both a and b
Answer:D
What is the Cambrian explosion?
A. An evolutionary period that began 540 million years ago B. A period when a large number of new animals appeared C. Neither a nor b D. Both a and b