What overall role does DNA play in the body?

DNA plays a fundamental role in controlling cell functions within the body. It serves as the genetic blueprint that dictates how cells operate, including the synthesis of proteins which are crucial for various cellular activities. Proteins perform a vast array of functions, such as catalyzing biochemical reactions (enzymes), providing structural support, and regulating gene expression. By determining which proteins are made and in what quantities, DNA effectively orchestrates a cell's activities and responses to the environment.

The other options do not accurately describe the primary function of DNA. While DNA is crucial for overall cellular integrity, it does not serve a direct protective role. It does not provide energy directly; energy in biological systems is primarily derived from metabolic processes involving carbohydrates and fats. Similarly, while proteins are involved in muscle building, DNA itself does not build muscle. Instead, it encodes the instructions for the synthesis of the proteins necessary for muscle development and repair. Thus, option B correctly captures the essential role of DNA in the body.