The Inset in the Figure Below Shows Halobacterium, an Archaean

The inset in the figure below shows halobacterium, an archaean that lives in environments with very high salinities.
What hypothesis can explain the extreme habitats of the archaeans?

A) They came to earth from other planets, where harsher conditions prevail.
B) They would be more widespread, but are unable to successfully compete with bacteria and now occupy habitats where bacteria cannot live.
C) Archaeans evolved when Earth was much less hospitable, and are now relegated to those habitats most similar to early Earth.
D) Numerous food resources are available and unexploited in Earth's extreme habitats.