Answer:
The correct answer is "Natural killer".
Explanation:
Natural killer cells, also known as NK cells or large granular lymphocytes, are cells that have an essential role in the innate immune system. Nk cells perform immunological surveillance, and are important for prevent the growth of tumors and develop chancer. Nk cells are able to recognize targets that are only present in cancerous cells, killing them before they start to proliferate.
