Meaning of happy-go-lucky

Test No. [color=blue]incompl/inter-93 “Hotchpotch”, question 4

He’s the sort of person who never worries about anything and has a happy disposition.

(a) over-heels
(b) tempered
© disposed
(d) go-lucky

Test No. [color=blue]incompl/inter-93 “Hotchpotch”, answer 4

He’s the sort of person who never worries about anything and has a happy go-lucky disposition.

Correct answer: (d) go-lucky

Your answer was: [color=red]incorrect
He’s the sort of person who never worries about anything and has a happy tempered disposition.
[size=200]_________________________[/size]

go lucky disposition? pls expain…
Also, what happens when I lose the dash here?

Happy go-lucky (or happy-go-lucky) is an adjective meaning carefree, free of responsibilities, cheerful. It’s usually written with one or even two hyphens for more clarity.[YSaerTTEW443543]

TOEFL listening discussions: A conversation between two students in their first class of the term[YSaerTTEW443543]

Kind of American “easy going” isn’t it?