Which of the following describes a reason why companies irradiate some fruits and vegetables before they are sold to the public? OPTIONS:
- to improve the flavors by increasing the sugar content
- to speed up the ripening of produce picked too early
- to partially cook the produce before canning or freezing
- to extend the shelf life by killing existing microorganisms
A: to extend the shelf life by killing existing microorganisms

Which of the following is most likely to make a rock crack and crumble? OPTIONS:
- dew evaporating on the rock
- leaves decaying on the rock
- snow melting in a crack in the rock
- water freezing in a crack in the rock
A: water freezing in a crack in the rock

Which of these is an organism that is unicellular? OPTIONS:
- virus
- amoeba
- mushroom
- ant
A: amoeba

Which of the following is a characteristic of all chemical changes? OPTIONS:
- A different state of matter is produced.
- Some mass is converted to energy.
- Some form of light is given off.
- A new material is formed.
A:
A new material is formed.