What underground part of a plant is responsible for absorbing nutrients and water?

The roots are the underground parts of a plant primarily responsible for absorbing nutrients and water from the soil. This absorption is crucial for the plant's overall health, as it relies on these nutrients and water to grow, thrive, and carry out photosynthesis through its leaves. Roots also anchor the plant in the ground, providing stability and support.

In the context of plant structure, stems, leaves, and stalks have different functions. Stems support the plant and elevate leaves for better sunlight access, while leaves are involved in photosynthesis. Stalk is another term often used for stems or parts of specific plants but does not contribute to nutrient and water absorption like roots do. Hence, the roots' specialized structure and function make them the correct choice for this question.