Please advise how to change the following sentence so that it would refer to the 3rd person of unknown sex (as an additional constraint, we need to start the sentence with "The other person"):
I am active and I like to keep myself busy; I often feel bursting with energy
It's straightforward but a bit long using "he" or "she":
The other person is active and he or she likes to keep him- or herself busy; he or she often feels bursting with energy
What about using "they" as they sometimes do:
The other person is active and they like to keep themselves busy; they often feel bursting with energy
The other person is active and likes to keep themselves busy; they often feel bursting with energy
Does any of the sentences sound OK to a native speaker? Would you understand that the question refers to a single person, not a group of persons? Which version ("he or she" vs "they") is easier to read?