Question

What key idea does the text below suggest?

Answer 1

The passage does mention that humans are vain and proud, but it's not the main argument, rather it's used as in introduction to the other idea: that humans did not imagine life outside of earth. So this pride prevented them from imagining life outside of Earth ("beyond its earthly level")

Therefore, the best option is the following one:
Pride kept humans from imagining life beyond Earth.