Problem:OPTIONS:
- hygeine
- emissions
- animals
- growth
- forces
- health
- education
- people

Fact 1: Population density is the average number of individuals per unit of area or volume. Fact 2: Another measure of growth is population density. Given the two facts above, what can be determined by the average number of people per one unit of area?
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A: growth

Problem:OPTIONS:
- trees
- oil
- deserts
- habitat
- solar
- air
- coal
- rocks

Fact 1: Cutting down trees has a negative impact on an ecosystem. Fact 2: An example is the uncontrolled cutting of trees for fuel. Given the two facts above, uncontrolled use of what for fuel has a negative impact on an ecosystem?
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A: trees

Problem:OPTIONS:
- our planet
- organisms
- Earthworms
- Flowers
- Echinoids
- toughness
- support
- cellulose

Fact 1: Agreenhouse is used to protect plants by keeping them warm. Fact 2: Flowers are the major greenhouse crops. Given the two facts above, what are the major crop that needs protecting by keeping them warm?
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A: Flowers

Problem:OPTIONS:
- Fruits
- stems
- roots
- pollen
- sheep
- bushes
- bees
- plants

Fact 1: Flowers attract animal pollinators. Fact 2: Bees are effective pollinators. Given the two facts above, what do flowers attract?
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A:
bees