"I am fine."
Translation:मैं ठीक हूँ।
It seems as if the difference between ha and hum ( I apologize for not spelling the two correctly) depends on whether the speaker is a boy or a girl. Thus both options can be correct when the question does not indicate the gender of the person making the statement. Or have I misunderstood?
No, हूँ is for 1st person singular regardless of gender.
मैं लड़का हूँ / मैं लड़की हूँ
मैं चाय पीता हूँ / मैं चाय पीती हूँ
है is used with तु (2nd person singular impolite), and with वह/यह (3rd person singular)
हो is used with तुम (2nd person singular)
हैं is used with आप (2nd person singular polite), and with हम/वे/ये (plurals, in either 1st, 2nd, or 3rd person)
I hope that helps :)