Which of the following types of letters is primarily used for business in the Navy?

The choice of a business letter as the correct answer is based on its specific purpose and format within naval correspondence. Business letters are typically utilized for formal communication related to business matters, such as requests, inquiries, and official announcements. They adhere to established guidelines and standards that ensure clarity and professionalism, which are crucial in maintaining effective communication within a military context.

In the Navy, these letters often follow a particular structure, including the sender's and recipient's addresses, an appropriate salutation, the body of the letter, and a formal closing. This format helps convey serious information or decisions, such as administrative directives or logistical requests, while also ensuring that the message is presented in a clear and direct manner.

Other types of letters, like formal letters, can overlap in purpose with business letters, but they may not strictly focus on business-related content. Notification letters are typically used to inform recipients about specific matters or actions without the formalities of a business letter. Informal letters, on the other hand, are used for casual communication and lack the rigidity and structure required in a military setting.

Thus, business letters serve as the primary mode for formal correspondence concerning professional matters in the Navy, making this option the best choice in the context of the question.