Which of these is not one of "the pieces" of a traditional three-piece suit?

Question

Which of these is not one of "the pieces" of a traditional three-piece suit?

Answer 1

Something missing here; but a 3-piece man's suit consists, of pants, coat, and vest. Anything else is not traditional.

A 3-piece woman's suit consists, of pants or a skirt, coat, and an inner upper garment, one might be a vest. It can also be coat, pants, and skirt.

Answer 2

Shirt