Would happen if the blood fails to regulate temperature or defend against pathogens?

The answer is; A

In the lymph vessels,  a few lymphocytes ‘ patrol’ the tissues as they scan for antigens. When they detect an antigen, including surface antigens of rogue cells (cancer cells), the antigen-presenting cells (APCs) present this to the cognate lymphocytes turning them to effector cells (such as effector T-cells). The effector T- cells bind to the cancer cells and induce apoptosis.