(Q).
You are presented with the question "What prolongs the storage life of food in space?" and the following answer choices: - hydrogen and oxygen - preservatives - Dehydration - heating liquids - Fuel cells - heat energy - hard outer covering - layers of fat Now knowing that astronauts require preserved food for extended flights and preservatives are added to extend the shelf life, choose the best answer.
(A).
preservatives

(Q).
You are presented with the question "What kills bacteria?" and the following answer choices: - rays or beams - Plasma cells - Cooking - an electric stove - Petri dish - deal - phlange - evaporation Now knowing that plasma cells are activated B cells that secrete antibodies and antibodies kill bacteria, choose the best answer.
(A).
Plasma cells

(Q).
You are presented with the question "Trees have woody stems covered with what?" and the following answer choices: - heat energy - thin skin - protective skin - skinny cells - white skin - Chlorophyll - Organic compounds - looseness Now knowing that trees have woody stems covered with bark and on the outside is a protective skin of bark made mainly of cork, choose the best answer.
(A).
protective skin