These T cells recognize an antigen and initiate a rapid response to the antigen:

A. The appendix is an organ that contains lymphoid tissue and plays a role in immune function, but it does not specifically refer to macrophages and monocytes.
B. The reticuloendothelial system (also known as the mononuclear phagocyte system) consists of macrophages and monocytes found throughout the body. These cells are part of the immune system and are responsible for phagocytosis, or the engulfing and digesting of pathogens, dead cells, and debris.
C. Peyer's patches are clusters of lymphoid tissue found in the small intestine that monitor and respond to pathogens in the digestive tract.
D. Tonsils are lymphoid tissues located in the throat, playing a role in immune defense, but they are not part of the reticuloendothelial system.

A. Red blood cells are not typically found in lymph. Lymph is a clear fluid that circulates through the lymphatic system and normally does not contain red blood cells unless there is damage or leakage from blood vessels.
B. Proteins can be present in lymph, especially smaller ones that pass through capillary walls.
C. Water is a major component of lymph, making up the fluid part that helps transport cells and substances.
D. Lymphocytes are a key component of lymph, playing a central role in the immune response.