Question

you would want a controlled-fusion power reactor near the ocean because of the abundant supply of deuterium and ____ hydrogen in ordinary water.

Explanation:

In ordinary water, the hydrogen isotopes present are deuterium and protium (also known as normal hydrogen or just hydrogen, with the atomic symbol \(^1_1H\)). For a controlled - fusion power reactor, along with deuterium, protium (or just hydrogen in the context of water's hydrogen content) is abundant in water. The most common hydrogen isotope in water is protium, so the blank should be filled with "protium" (or "normal" can also be used in a more general sense, but "protium" is the correct isotopic term).

Answer:

protium