Final answer:
T cells, specifically killer T cells, are the types of blood cells that kill cancer cells. They are activated when they encounter infected or cancerous cells and release toxins to destroy them.
Step-by-step explanation:
The types of blood cells that are involved in killing cancer cells are white blood cells, specifically T cells. T cells, also known as T lymphocytes, are a type of white blood cell that plays a crucial role in the immune response. Killer T cells, or cytotoxic T cells, are activated when they encounter cells infected with pathogens or cancerous cells. They then release toxins to kill the infected or cancerous cells, helping to eliminate the threat.