Direction: Read the following passages carefully and answer the question that follows.
An iron or steel bridge swells (gets larger) when warmed by the Sun and shrink (gets smaller) when it becomes colder. Heat makes everything expand and cold makes everything contract. Cold is the absence of heat. Metals change their size when heated or cooled and this change is noticeable in a bridge that is made of iron or steel. The builder of a bridge must leave empty spaces for the metal to expand into. Have you noticed that concrete sidewalks have cracks every few feet ? These cracks provide space for the concrete to expand into when heated.