Which of these plants doesn't belong to the wild cabbage species Brassica oleracea?

Brassica oleracea or wild cabbage is a plant species that includes many common foods as cultivars, including cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, savoy, kohlrabi, and gai lan.

Kohlrabi, also called German turnip, is a biennial vegetable, a low, stout cultivar of wild cabbage. Broccoli is an edible green plant whose large flowering head and stalk is eaten as a vegetable. Cauliflower is a vegetable the head of which is composed of a white inflorescence meristem.

Celery (Apium graveolens) is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, leaves or hypocotyl are eaten and used in cooking. Celery seed is also used as a spice and its extracts have been used in herbal medicine.

Apiaceae or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus Apium and commonly known as the celery, carrot or parsley family, or simply as umbellifers.