Final answer:
It is false to assume you can always use someone's first name; formal titles and last names are appropriate in professional settings until familiarity is established.
Step-by-step explanation:
It's false that you can always assume familiarity and call someone by his or her first name when addressing them. The appropriateness of using a first name depends on various factors, including cultural norms, the setting, and the relationship between the individuals. For example, in a business letter, it's important to use the recipient's title, and when addressing a healthcare provider, you would use a more formal mode of address unless directed otherwise. The social rules can be different depending on the context, like casually greeting someone in a grocery store or interacting in a professional environment.
In professional settings, it's customary to use formal titles or last names until a more familiar relationship is established or permission to use the first name is given. This level of formality helps maintain a professional demeanor and shows respect for roles and boundaries. However, in some modern workplaces and among younger individuals, using first names upon introduction is becoming more common, but one should always err on the side of caution and start with a formal address.