If you had to be referred to with a noun that specified your gender as an adult man (if you’re not adult yet, answer as if you were), how would you like to be designated?
The option “a male” here refers only to the word as a noun, not an adjective: the noun pluralized as “males.”
In even more comfortable terms, “That guy. You know, the bloke with the eyeglasses. That goofy-looking jasper. The cob with the eyebrows. Tough wight to beat at Scrabble. Nice fellow if you stay away from sex, politics, and religion. A fun dude to hang with.”
They are all fine, except perhaps for “boy” or “lad” which are pretty content specific. Here in the US of A, I’d tolerate those only from an Irishman or a Scot.
I chose ‘man’ because I am boring.
Though the meaning of ‘gentleman’ includes ‘well-educated’ and ‘of a good family and distinction’, I do not act the part often. And when I do, I am acting.
Not boy or lad as I am neither and I would be weirded out if someone in casual conversation referred to me as a male. “You’re a male, what do you think of [male-related thing]”=weird. I really only like male and female in adjectival use. (And I don’t care what anyone says about using nouns as adjectives. Stop saying woman instead of female. She is not a woman doctor, a woman cop, a woman coach; she is a female doctor, cop or coach unless you would refer to him as a man nurse, a man teacher or a man receptionist which to my horror, I have seen some people begin to do.)