Which substance should a student apply to the skin if he or she gets splashed with an acid? OPTIONS:
- water
- vinegar
- salt
- formaldehyde
A: water

Red-clay bricks have a density of approximately 2000 kg/m^3. Air has a density of 1 kg/m^3. Which of the following has the lowest mass? OPTIONS:
- 2 m^3 of bricks
- 4 m^3 of bricks
- 6000 m^3 of air
- 10,000 m^3 of air
A: 2 m^3 of bricks

Humus is an organic material that makes up soil. Which characteristic best indicates that soil has a high humus content? OPTIONS:
- the color of the sample
- the mass of the sample
- the amount of clay in the sample
- the amount of rock in the sample
A: the color of the sample

What part of an atom orbits around the center of the atom? OPTIONS:
- proton
- nucleus
- neutron
- electron
A:
electron