Think about the article. When it's cold outside, an Earthship stays warm inside because it has __ A. thick walls B. an indoor garden C. water tanks D. a curvy shape

## Step 1<br />The question is asking us to identify the feature of an Earthship that helps it stay warm during cold weather. An Earthship is a type of sustainable, eco-friendly housing made from natural and recycled materials. <br /><br />## Step 2<br />Option A suggests that the thickness of the walls is the reason for the warmth. This is a plausible explanation because thick walls can act as insulators, reducing heat loss and thus maintaining a warm temperature inside the Earthship.<br /><br />## Step 3<br />Option B suggests that an indoor garden is the reason for the warmth. While an indoor garden can contribute to a warm and cozy environment, it doesn't necessarily contribute to the overall warmth of the Earthship.<br /><br />## Step 4<br />Option C suggests that water tanks are the reason for the warmth. Water tanks can help to regulate the temperature inside the Earthship, but they don't necessarily contribute to the overall warmth.<br /><br />## Step 5<br />Option D suggests that a curvy shape is the reason for the warmth. The shape of the Earthship can contribute to its overall energy efficiency, but it doesn't necessarily contribute to the warmth.