Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 31 to 35.

In the 1970s, many people became concerned about energy. People had to face up to the fact that they used too much energy, and energy sources were not going to last forever. One architect, Michael Reynolds, decided to do something. He set out to design homes that were cheaper to build and more energy efficient. In addition, he wanted to do something about all the garbage. Finally, he came up with the idea of “earthships.” Although it sounds like a boat, an earthship is a house. However, unlike regular houses, earthships are constructed from garbage and are built using only ten percent of the energy needed to build a typical house. Moreover, after they are built, earthships use only ten percent of the energy required to heat, light, and cool a regular home. Although earthships sound unique, they can actually be built to look just like any other house. One of the big benefits of earthships is that they are made from recycled materials. The main construction material of an earthship is used tires that are filled with dirt. The dirt-filled tires are then laid flat and stacked like bricks. Because the tires are round, there is lots of extra space between the columns of tires. These spaces are filled with used cardboard. The tires and cardboard form the outside walls of an earthship. Another benefit of an earthship is that it saves energy and natural resources. For example, an earthship uses less water. Rain water, which is collected on the roof, is used for drinking and bathing. All of these features make earthships very environmentally friendly. That’s one of the reasons they have become popular throughout the world. Earthships have been built in Bolivia, Australia, Mexico, Japan, Canada, England, Scotland, and all over the US. Maybe in the near future, an earthship will be landing near you! (Adapted from Reading Challenge 3 by Casey Malarcher and Andrea Janzen) 

Which best serves as the title for the passage?