Which substances are particularly important in forming the structures of the cell ?

Nucleic acid certain protein cell membranes certain carbohydrates

Which best explains how a heat pump can heat a room? cold air from the house is moved through pipes, where it absorbs thermal energy. warm air from outside is pushed into the house to replace the cold air. combustion warms the air when chemical energy is transferred to thermal energy. fuel is used to move a piston, which pushes warm air into the house.

Regarding most of the narrator’s story, which word best describes the tone?