From the understanding of how water moves through plants, the only circle that can have a downward pointing arrow only is A.
Water moves through a plant in the following direction:
Soil ----> root -----> stem ----> leaves
Once water gets into the root from the soil, a conducting tissue known as xylem conducts the water upward through the stem of the plant branching off into the leaves through the petiole. from the petiole, water is then conducted to the mesophyll cells.
Circle D represents the root, so the arrow must be upward.
Circle C represents the stem, the arrow continues upward towards the leaves
Circle A and B represent the leaf. The movement of water within the leaf might requires that it is from circle A to circle B. Hence, the only circle that must have an arrow pointing downward only can only be A.
More on the movement of water through a plant can be found here: https://brainly.com/question/11903396
