Which of the following is an example of a broadleaf weed?

Common ragweed is categorized as a broadleaf weed due to its distinctive leaf shape and structure, which are wider and flatter compared to the narrow, linear leaves typical of grass species. Broadleaf weeds are generally characterized by having a broad, flat leaf blade and a branched growth habit, which allow them to compete effectively with crops for sunlight, nutrients, and water. Common ragweed, in particular, is also notorious for its ability to produce a great number of seeds that can persist in the soil, making it a resilient and often problematic weed in many agricultural settings.

In contrast, the other options refer to grass-type plants, which have slender and elongated leaf blades. Quackgrass and crabgrass are both grass species, as is Timothy, which is a cultivated grass commonly used for hay and pasture. These differences in leaf structure and growth forms determine the classification of these plants as either broadleaf or grass, with common ragweed clearly fitting the broadleaf category.