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

The roots of a plant play a crucial role in absorbing nutrients and water from the soil. They are specialized structures designed to take in these essential resources, which are vital for the plant's growth and overall health. Roots also anchor the plant securely in the ground, providing stability, and they can store energy and nutrients in some species.

In contrast, the stem serves primarily to support the plant and facilitate the transportation of nutrients and water between the roots and leaves. Leaves are responsible for photosynthesis, capturing sunlight to convert it into energy, while the stalk is generally a term used for the main stem or a supporting structure for flowers or fruits. None of these functions involve the direct absorption of water and nutrients from the soil, making the roots the correct choice in this context.