What is true about grasses?

Grasses are characterized by having straight leaves with parallel veins, which is a fundamental trait of monocots. This leaf structure is essential for the way grasses photosynthesize and adapt to various environments. The parallel vein pattern allows for efficient transport of nutrients and water throughout the leaf, aiding in their growth and survival in different conditions.

In contrast to the other options, grasses do not possess broad leaves; instead, their leaves are generally narrow and elongated. While grasses can grow in arid conditions, they are also found in a wide range of environments, including wetlands and temperate forests, thus making the assertion of their growth being limited to arid conditions inaccurate. Additionally, grasses develop deep and extensive root systems that help them access water and nutrients, providing stability and resilience, further underlining the misinformation in the claim that they do not have root systems. Overall, the defining characteristic of their straight leaves and parallel veins is what makes option C the correct choice.