Sound waves travel fastest in OPTIONS:
- air.
- iron.
- water.
- a vacuum.
A: iron.

Which two systems are involved when waste and water are removed from blood as it flows through the kidneys? OPTIONS:
- respiratory and circulatory
- digestive and respiratory
- digestive and urinary
- urinary and circulatory
A: urinary and circulatory

A simple food chain includes hawks, lizards, and insects. Which will most likely happen to the lizard and hawk populations if a pesticide is sprayed to kill the insects, and the lizard and hawk populations cannot find other food in this ecosystem? OPTIONS:
- Both the lizard population and the hawk population will increase.
- Both the lizard population and the hawk population will decrease.
- The lizard population will increase, but the hawk population will decrease.
- The lizard population will decrease, but the hawk population will increase.
A: Both the lizard population and the hawk population will decrease.

Sooj learned that whales use vocalization to navigate and to communicate with other whales. Some scientists think that noise pollution in whale habitats may harm whale populations. What would be the most likely effect of noise pollution on whales? OPTIONS:
- alteration of whale genetic material
- reversed flow of energy through whale habitats
- reduced populations of food organisms in whale habitats
- separation of whale family groups
A:
separation of whale family groups