Which process causes Earth’s surface to warm? the conduction of heat by air above Earth's surface
the radiation of the Sun’s electromagnetic waves
the convection of warm air from the atmosphere
the reflection of electromagnetic waves off bodies of water

Which statement correctly describes a step-up transformer? a. it increases the amount of electric energy available. b. it increases the voltage of an electric current. c. it changes direct current into alternating current. d. it has more loops of wire in its primary coil.