Which feature is associated with grasses?

The feature associated with grasses is round, hollow stems and narrow, parallel-veined leaves. This characteristic is a defining trait of grasses, which belong to the family Poaceae. Grasses typically exhibit a growth habit that includes these hollow stems, allowing them to grow tall and resilient, especially in their natural environments. The narrow, parallel-veined leaves further distinguish grasses from other plant types that may have broader leaves or different vein patterns.

While the other options describe features associated with other plant types—solid stems with broad leaves might be indicative of broadleaf plants, square stems could refer to plants in the mint family, and serrated leaves are often seen in various herbaceous or woody plants—these features are not representative of grasses. In contrast, the unique combination of round, hollow stems and narrow leaves with a parallel vein structure is a clear identifier of grass species.