Which of the following flowers is NOT included in the list of line flowers?

Line flowers are characterized by their long, straight stems and are often used in floral arrangements to create height and structure. Among the options provided, sunflowers do not fit into this category.

Sunflowers are typically categorized as form flowers due to their bold heads and large blooms, which serve as focal points in arrangements rather than contributing to the linear structure. In contrast, flowers like stock, curly willow, and bells-of-Ireland are recognized for their elongated shapes and are commonly utilized to add verticality and elegance in floral design.

By understanding the characteristics that define line flowers, it becomes clear that sunflowers' distinct form and role in arrangements differentiate them from the others listed, solidifying their status as not belonging in the line flower category.