The correct answer is C. root hairs.
Root hairs are tiny, thread-like projections that extend from the root tips of plants. They are very important for water absorption because they have a large surface area in contact with the soil. This allows them to absorb water and minerals from the soil very efficiently.
The embryonic zone is the region of the plant embryo that gives rise to the root and shoot. It is located at the tip of the embryo and is not involved in water absorption.
The growing point is the region of the plant where new cells are produced. It is located at the tip of the stem and is not involved in water absorption.
The zone of elongation is the region of the plant where cells elongate. It is located just behind the growing point and is not involved in water absorption.
In conclusion, plants absorb most part of water needed by them through their root hairs.