This selection is mainly about the A engineering used to build some of the la A structures. (B) effects on the environment of large man. B structures. C risks and rewards of becoming a builder c made structures. D properties of heat and light and the rela D between them.

## Step 1<br />The problem is a reading comprehension question. The task is to identify the main idea of the selection. The main idea is the primary concept or point that the author wants to convey to the reader.<br /><br />## Step 2<br />The options provided are:<br />A. engineering used to build some of the large structures.<br />B. effects on the environment of large man-made structures.<br />C. risks and rewards of becoming a builder of structures.<br />D. properties of heat and light and the relation between them.<br /><br />## Step 3<br />The correct answer is B. The selection is mainly about the effects on the environment of large man-made structures. This is the main idea that the author wants to convey to the reader.