Prior to 500 million years ago, organisms were

unable to venture onto land because
a. the earth’s crust was too hot.
b. the land was too dry.
c. there was not enough oxygen in the atmosphere
for respiration.
d. the land was not shielded from the sun’s
ultraviolet radiation.
e. there was no organic matter on land for food


Answer: d

Biology & Microbiology

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