Which of the following identifies the hepatic flexure?

a. Produce chemicals that regulate the level of the immune response: While some T-cells can secrete cytokines that regulate the immune response, this is not the primary function of helper T-cells.

b. Recognize foreign antigens and initiate an immune response. Helper T-cells (Th cells) are a type of lymphocyte crucial in cell-mediated immunity. They play a central role in recognizing and identifying foreign antigens (substances recognized as foreign by the immune system). Once they recognize an antigen, they activate other immune cells like cytotoxic T cells and B cells to mount an immune response.

c. Chemically destroy foreign antigens by disrupting cell membranes: This is the function of cytotoxic T cells, not helper T-cells.

d. Create antibodies to target foreign antigens: Antibody production is the function of B cells activated by helper T-cells.

a. Carrying stimulus to the spinal cord and the brain from all other parts of the body: This is the function of afferent neurons, not efferent neurons.

b. Conducting impulses from sensory neurons to motor neurons: This describes interneurons, which relay signals between sensory and motor neurons.

c. Regulating neuron function: This is a vague description and doesn't specifically relate to the primary role of efferent neurons.

d. Carrying stimulus away from the brain and spinal cord: This correctly describes efferent neurons, which carry motor commands from the central nervous system to muscles and glands.