What is the name of the black round object in the sandwich in the picture? Solve it ~ ~

This is an "undersea sandwich", and the black one is olive ~

Sub, also nicknamed "torpedo", is an Italian-American sandwich. Rectangular bread loaf (usually Italian or French bread) is used as the bottom, cut in half longitudinally, and sandwiched with various meats, cheeses, vegetables, spices and sauces [1][2]. In the United States, there is no common name for submarine sandwiches. The names of major cities are different [1], and the word "submarine sandwich" is widely known. It is generally believed that the word "submarine" originated from a restaurant in Sculley Square in Boston, Massachusetts, USA during World War II.

Materials:

1, sliced bread or rectangular bread

2. Lettuce; lettuce

3. sweet pepper

4. Olives

5. onions (surname)

6. Cucumber

7.pickled cucumber

8. Pickled jalapenos

9. tomatoes

10, salad dressing

I hope the above answers can help LZ. O(∩_∩)O ha!