Perennial weeds are difficult to control because they have:

• A. Persistent root system
• B. Shallow root system
• C. No roots
• D. High photosynthetic rate

Answer: (A)

The main idea here is that perennial weeds are hard to control because their underground parts are persistent and capable of storing energy. These plants survive above-ground removal by relying on their root systems, crowns, rhizomes, tubers, or other underground structures to resprout. Even after mowing, tilling, or herbicide application, the stored carbohydrates in these roots keep the plant alive and ready to grow again, so control measures must deplete those reserves over time or remove the underground parts as well. That storage-and-regrowth ability is what makes perennials tougher to eradicate.

A shallow root system wouldn’t provide the same resilience, and having no roots would describe annuals that die after seeding. A high photosynthetic rate might help growth, but it doesn’t by itself explain why the plant persists after above-ground damage.