Part A A. In "Earthships," what can be inferred about why people would use passive solar?

B. It aids in the collection of "gray" water.

C. It is the only viable source of heat on an Earthship.

D. It is a superior source of natural gas.

It is an economically practical alternative to electricity.

Part B

Which evidence from the passage best supports the answer to Part A?

A. "Now, long-term studies have revealed some problems. For one, without sufficient sunlight during the winter, large amounts of natural gas known as propane and/or wood are used to heat the home. "

B. "During the summer, the combination of the cool temperature of the earth beneath the floor plus the thick walls can keep the house comfortable without the use of air-conditioning."

C. "Building an Earthship may be an attractive choice for those who want to use fewer of our planet’s non-renewable resources."

D. "Floor-to-ceiling windows on an Earthship's south wall also allow plenty of sunlight."