What type of correspondence should contain detailed instructions for action?

The correct choice is based on the fact that controlled correspondence is specifically designed to provide detailed instructions and guidance for actions that must be followed. This type of correspondence is typically used in contexts where clarity and precision are essential, such as in orders or directives that require compliance with specific protocols.

Controlled correspondence ensures that the recipient clearly understands the expectations and necessary steps they need to take. This is particularly important in military operations where exactness can impact mission success and safety. By containing detailed instructions, controlled correspondence minimizes the risk of misinterpretation or error.

In contrast, informal correspondence would not typically contain the structured or detailed instructions that are characteristic of controlled correspondence. General correspondence may provide routine information, while preliminary correspondence usually serves as an introductory notice rather than a detailed directive, making them less suited for conveying specific actions.