Nutrition

The governing concept is saprophytic, or extracellular, digestion. Fungi secrete digestive enzymes onto dead and decaying organic matter. These enzymes break complex substances into simpler, soluble molecules outside the fungal body; the hyphae then absorb those molecules. Fungi do not use lungs, make food from blood, or produce chlorophyll in leaves. Thus the release of digestive juices outside the body directly explains their mode of nutrition.

Digestion breaks food into small molecules, but the body can use them only after absorption. Villi normally increase the intestinal surface area and provide thin routes into blood and lymph. If villi are damaged, less glucose, amino acids, fatty-acid products, vitamins, and minerals enter circulation, causing poor nourishment and weakness even when food is eaten. Hence option A is correct.

The governing concept is parasitic nutrition and the role of chlorophyll. Green colour generally indicates chlorophyll, the pigment needed to capture light for photosynthesis. Cuscuta has little or no chlorophyll, so it cannot manufacture sufficient food from carbon dioxide and water. It obtains nutrients from a host plant through specialised absorbing structures. Thus option A is correct; the other choices mention increased photosynthesis or organs absent from plants.