What are three functions of a leaf?

they contain chlorophil, vital for absorbing sunlight to photosynethise - making 'food' for the plant.

they catch water from rain, and it drains from here to the roots, to be soaked up.

some plants can clone, making one stem identical to the whole plant, so the leaves can be cloned too, meaning there is more room for photosynthesis to take place.

hope this helped.