Given a scientific passage and an answer, generate a question for the given answer.

Passage: The Universe contains about a hundred billion galaxies. Answer: about a hundred billion
Approximately how many galaxies are there in the universe?

Passage: Bacteria change nitrogen gas from the atmosphere to nitrogen compounds that plants can absorb. Answer: bacteria
What changes nitrogen gas from the atmosphere to nitrogen compounds that plants can absorb?

Passage: Six atoms are evenly organized around a central atom. Answer: six
How many atoms are evenly organized around a central atom?