Which organization serves as the United States representative to ISO?

The American National Standards Institute (ANSI) serves as the U.S. representative to the International Organization for Standardization (ISO). ANSI's role is crucial as it oversees the development of voluntary consensus standards for various industries and ensures that the U.S. viewpoint is represented in the formulation of ISO standards. This is essential for maintaining the country's competitiveness in global markets and ensuring that U.S. products and services can be recognized and accepted internationally.

In contrast, while organizations like the National Institute of Standards and Technology (NIST), ASTM International, and the Occupational Safety and Health Administration (OSHA) play significant roles in standards development and safety regulation, they are not the primary entities representing the U.S. in ISO-related matters. NIST focuses on developing measurement standards and technology, ASTM is involved in developing technical standards for materials and processes, and OSHA regulates workplace safety.

Thus, ANSI's specific function as the U.S. representative to ISO identifies it as the correct answer to the question.