The correct answer is A. Xylem.
Xylem is a vascular tissue in plants that transports water and minerals from the roots to the leaves. It is made up of dead cells that have thick walls and are arranged in long, narrow tubes. The water and minerals are transported through these tubes by osmosis, a process in which water moves from an area of high water concentration to an area of low water concentration.
Phloem is another vascular tissue in plants that transports food from the leaves to the other parts of the plant. It is made up of living cells that have thin walls and are arranged in long, narrow tubes. The food is transported through these tubes by a process called translocation, which is a combination of diffusion and active transport.
Cortex is the layer of cells that lies between the phloem and the xylem. It is made up of living cells that have thin walls and are arranged in a loose network. The cortex helps to protect the plant and to transport water and minerals.
Cambium is a layer of cells that lies between the xylem and the phloem. It is made up of dividing cells that give rise to new xylem and phloem cells. The cambium is responsible for the growth of the plant in thickness.