Cytotoxic t-lymphocytes produce a substance called

Cytotoxic T lymphocytes make a substance called perforins,granzymes, FasL

Explanation:

Cytotoxic T lymphocytes (CD8 +) recognize infected cells and destroy them by secreting molecules that activate apoptosis of the target cell (substances such as perforins, granzymes, FasL)

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.