Final answer:
True. A letter is an effective channel for formal and sensitive internal written messages. Business letters are often used for formal correspondence with companies, politicians, and institutions, and can yield a favorable response for refund requests or job inquiries.
Step-by-step explanation:
True. A letter is indeed an effective channel for an internal written message requiring formality or sensitivity. Business letters are often used for formal correspondence and are appropriate when communicating with companies, politicians, and institutions. They are more likely to result in a favorable response when requesting a refund for a faulty product or inquiring about a job opening.