What is the main difference between natural killer cells & T cytotoxic cells?

• A. Natural killer cells do not need to be activated to target & kill infected host cells, but T cytotoxic cells do.
• B. T cytotoxic cells do not need to be activated to target & kill infected host cells, but natural killer cells do.
• C. T cytotoxic cells bind to antibodies on the surface of host cells & natural killer cells do not.
• D. Natural killer cells are a part of the adaptive immune response & T cytotoxic cells are innate lymphocytes.