The houses we live in are very important. They keep us from being cold in the winter and hot in the summer. In the winter they keep out the snow. They also keep out the wind. Even if it is blowing outside, we are nice and warm inside. In the summer houses keep the hot sun from us. When it rains, they keep us from getting wet. Houses are also places where we can feel safe. People can’t get at us or our things. Houses give us a place to be together with our families and friends. Mothers and fathers care for their children there. The children play there. The family eat and sleep under the same roof. Houses are different in many ways. They are made of different things. Some houses are made of wood. Some are made of stone. Sometimes more than one thing is used to make a house. Houses come in different sizes. Some houses have only one room. Some houses have more than one room. Big apartment houses found in cities have a great many rooms. They hold many families. The rooms in which each family lives are called an apartment. Houses are different in the ways they are built. Houses in hot countries can be lightly built. In places it rains much of the time, houses must keep out the water. Which of the following probably is NOT the thing used to build houses