How were conditions on the early Earth of more than 3 billion ...

[penguins]

How were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?
A) Only early Earth was intensely bombarded by large space debris.
B) Only early Earth had an oxidizing atmosphere.
C) Less ultraviolet radiation penetrated early Earth's atmosphere.
D) Early Earth's atmosphere had significant quantities of ozone.

[Millan]

I know it's A, we did this last month

[penguins]

Thank you, thank you!!