Which sample was most likely DNA?

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.

In the diagram below, the northern hemisphere would be in what season at position a a.fall b. winter c.summer d.spring

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?