At least one of (1)A B C appears: ω-A' B' C'

(2) There is only one 2)AB C: A 'B 'C+A 'BC'+AB 'C'

(3) At most one event occurs in ABC: A'B'C'+A'B'C+A'BC'+AB'C' (2) but ABC colleagues do not.

(4) Appears at least twice in ABC: ABC'+A'BC+AB'C+ABC (equal to appearing twice in ABC plus ABC).

Ω-ABC (no more than 2 times, that is, three times at the same time)

⑸A ' b ' c

Note: Expressions are not unique.