Informal institutions are unwritten social constraints that shape behavior, including norms, customs, values, traditions, and ethics. Option B is correct because ethics represents an informal guide to behavior rather than a formally codified legal requirement. Informal institutions reduce uncertainty by helping people understand what is socially acceptable, trustworthy, or legitimate in a particular society. They matter greatly in global business because managers may comply with formal laws but still fail if they ignore local customs or ethical expectations. Rules and regulations are usually formal when written and enforced by legal authorities. Written laws are clearly formal institutions. Informal institutions are enforced mainly through social approval, reputation, relationships, and cultural expectations rather than courts or government penalties.