Practice question

NaCl (B) is the right choice. This sits at the heart of Excretory System: the wording points straight to what is happening in the tissue or organ system. A useful study habit is to ask what the structure or process is for: NaCl is the option that correctly names the structure, process, or principle asked for in Excretory System. That reasoning supports NaCl. One solid sentence about why this works is enough for recall — you do not need a long essay for every MCQ. When you practise, cover the choices first, write NaCl from memory, then reveal the letter — that habit builds real recall for Excretory System.