Which vegetable is known for its round shape and strong smell?

Onions are well-known for their distinctive round shape and strong, pungent aroma. This characteristic smell is due to the presence of sulfur compounds, which are released when the onion's cells are broken down, such as during chopping or slicing. The strong smell can often cause tears when the onion is cut, making it one of the most recognizable traits of this vegetable.

In contrast, tomatoes, peppers, and carrots do not have the same round shape or strong smell associated with onions. Tomatoes are typically more oval or round, but they have a sweet and mild aroma. Peppers come in various shapes, often more elongated or bell-shaped, and have a fresh, sometimes spicy smell, but lack the strong odor characteristic of onions. Carrots are long and taper towards one end, with a subtle and earthy aroma that is not as strong as that of onions. Thus, the unique combination of round shape and strong scent makes onions the correct choice.