What is the clear yellowish fluid that carries disease-fighting cells called lymphocytes?

The correct answer is lymph, which is a clear yellowish fluid that is essential in the body's immune response. Lymph is part of the lymphatic system and is responsible for transporting lymphocytes, the cells that play a crucial role in fighting infections and diseases. The lymphatic system helps to maintain fluid balance in the body, filtering lymph through lymph nodes where immune responses can be activated against pathogens.

Blood, while it also transports cells, nutrients, and waste, is not specifically composed of lymphocytes exclusively, nor is it yellowish and clear in color; it contains red blood cells, which give it a different color. Plasma is the liquid component of blood that carries nutrients, hormones, and waste products, but it is not the same as lymph and primarily contains blood cells rather than lymphocytes specifically. Serum, which is the clear fluid that remains after blood has clotted, also does not function the same way as lymph and does not transport lymphocytes in the same context.

Understanding the role of lymph in the immune system highlights its importance in keeping the body healthy and responding to foreign invaders effectively.