a. It allows us to re-use products instead of manufacturing new ones.

b. It prevents garbage from being burned.

c. It saves on the amount of fuel used by garbage trucks.

d. It saves on the amount of plastic used to manufacture garbage bags.

a. All non-renewable resources pollute the environment; renewable resources don't.

b. Non-renewable resources must be refined before humans can use them; renewable resources don't.

c. Non-renewable resources exist in unlimited quantities; renewable resources don't.

d. Non-renewable resources exist in limited quantities; renewable resources don't.

a. Most people chose not have children 200 years ago

b. People 200 years ago killed one another frequently

c. People 200 years ago had better medicine than we do today

d. People today live longer, healthier lives than 200 years ago

a. Recycling allows resources to be reused, instead of dumped in landfills.

b. Recycled products emit oxygen into the atmosphere.

c. Recycling causes the earth to cool down, instead of warm up.

d. Recycling turns non-renewable resources into renewable ones

a. They are gases created when wood is burned

b. They are gases that regularly escape from landfills

c. They are gases that contribute to global warming

d. They are examples of non-renewable resources

a. Turning your lights off when you're not using them.

b. Recycling newspapers.

c. Cleaning up the garbage in your neighborhood.

d. Turning up your thermostat whenever you feel chilly.

a. They are an alternative to non-renewable energy sources like fossil fuels

b. They are used by people in alternative communities

c. They use alternating current instead of direct current

d. You can alternate between using solar power during the day and wind power at night

a. Too many people breathing causes too much carbon dioxide to enter the atmosphere

b. The body heat generated by billions of people leads to an increase in global warming

c. More people being born means more paper is needed to print birth certificates

d. All people produce waste, so more people equals more waste

a. Ask your parents to buy you your own car

b. Try to reduce your consumption of electricity and fuel

c. Use only electric appliances in your home

d. Only buy products with vacuum-sealed plastic packaging

a. 14 million

b. 22 billion

c. Between 7 and 8 billion

d. 1.5 trillion