The correct approach is to use constructor dependency injection (DI) to obtain a logger instance. Option A properly declares a private property for the logger and injects Psr\Log\LoggerInterface through the class constructor. In Magento 2, the DI configuration (di.xml) is used to define which specific logger instance (in this case, the one configured for the 'contact' category) should be provided. This method adheres to Magento's architectural principles, promotes loose coupling, and ensures the pre-configured logger is used, making the code testable and maintainable.

1. Magento 2 Developer Documentation

Dependency injection: "Constructor injection is the preferred way to get a new dependency in your class... Magento automatically generates the necessary code for the constructor." This supports Option A as the standard method. (See Fundamentals -> Architectural deep-dive -> Dependency injection).

2. Magento 2 Developer Documentation

Technical Vision: "Do not use the ObjectManager directly... Using the ObjectManager directly hides the real dependencies of a class." This explicitly marks the method in Option B as incorrect. (See Best practices -> Technical guidelines).

3. Magento 2 Developer Documentation

Logging: The documentation explains that custom loggers are configured as virtual types in di.xml and then injected into classes via the constructor. This process relies on DI

making Option C (direct instantiation) an incorrect approach that ignores the framework's configuration. (See How-tos -> Customize logging).