The pull of gravity on Earth is caused by OPTIONS:
- air pressure.
- the mass of Earth.
- volcanoes erupting.
- Earth's orbit around the Sun.
A: the mass of Earth.

Which of these resources is renewable? OPTIONS:
- natural gas
- oil
- coal
- wind
A: wind

The energy required to lift an object is supplied by ATP derived from the breakdown of molecules of OPTIONS:
- glutamate.
- glycerol.
- glycolysis.
- glucose.
A: glucose.

The Milky Way Galaxy is visible as a bright region in the night sky. Modern telescopic observation has made it possible to discover that the brightness of the Milky Way Galaxy is due primarily to which structure? OPTIONS:
- clouds of hot gas
- large numbers of stars
- high energy compounds
- extremely reflective ice particles
A:
large numbers of stars