Cyt is the root of the combining form cytology, but it is not associated with fat. Gluc is a root of the combining form glucose, but it is not associated with fat. Lip is the root of the combining forms Lipids, Lipopolysaccharides, and/ or Lipase and it is associated with fat. Thus, leading to the conclusion that the answer is indeed Lip.
Please remember that it helps to provide the choices that match your question. This can help you get an accurate answer and have your question answered much quicker.
