Practice question

Go with B — Principal cells. Within Excretory System, that statement lines up with the standard definition and the usual exam wording you’ll see. In plain terms, Principal cells is the option that correctly names the structure, process, or principle asked for in Excretory System. Holding that picture in mind makes Principal cells feel natural rather than something you only memorise. Link the term to a real body example (organ, tissue, or ion flow) so the idea stays concrete under exam pressure. A short mental diagram helps — start from stimulus or structure, follow the pathway, and stop at the functional result described by Principal cells.