What is the maximum number of electrons that can be present in each principal energy level of hydrogen?

Each principal energy level has one sublevel containing one orbital, an s orbital, that can contain a maximum of two electrons.

Explanation:

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

i would say b

explanation:

but i think i would need more information than that