A.Death. | B.Evolvement. |
C.Presence. | D.Decrease. |
A.A shortage of clean water. |
B.A break in the food chain. |
C.A small variety of animals. |
D.The constant warming climate. |
A.Oceans became too hot for animals. |
B.There was less oxygen in the oceans. |
C.Earth's climate became violent. |
D.The majority of the plants gradually died out. |
A.the evolvement of mammals on Earth |
B.the gradual process of climate change |
C.the importance of the balance of ecosystem |
D.the cause of the extinction of the dinosaurs |