$1\mathrm{.}6$ How do you define an enumeration $(1)$

A$.$ enum Days $\{$ Sunday, Monday, Tuesday $\}$;

B$.$ enum Days: int $\{$ Sunday, Monday, Tuesday $\}$;

C$.$ enum Days $=\{$ Sunday, Monday, Tuesday $\}$;

D$.$ enum Days: string $\{$ Sunday, Monday, Tuesday $\}$;