Roots are the main organs for plants to absorb water and inorganic salts. From the top, the structure of roots is root cap, meristem, elongation, mature area and its upper part. Some cells in roots differentiate to form conduits, which can transport water and inorganic salts.

The common radish is the root of plant radish, which stores a lot of nutrients and has absorption function; Luffa and banana are fruits; Sweet potato is the root with absorption function, and the bud primordium on potato is the stem.

So choose B.