Option 1 is correct. Enabling garbage collection logging with JVM flags allows you to analyze memory usage patterns and identify memory leaks or excessive memory consumption, which are common causes of OutOfMemoryErrors. Increasing the number of application instances may exacerbate the issue if it's related to memory consumption. Disabling Spring beans or reducing threads may not be suitable solutions for addressing OutOfMemoryErrors.

In reactive programming with Spring Boot, you can handle errors in a reactive stream by using the onError operator and other error-handling operators provided by Project Reactor. These operators allow you to define how to react to errors within the stream, whether it's by logging, retrying, switching to a fallback stream, or propagating the error to the subscriber. This enables robust error handling and recovery strategies in reactive applications.

In Spring Boot unit testing with Mockito, you use the @InjectMocks annotation to inject mock objects into the object being tested. This allows you to control the behavior of dependencies during testing.

When developing a Spring Boot application with a large team, it's best to use Spring Boot's external configuration mechanisms like application.properties or application.yml files. These can be organized into separate folders or packages for each module, making it easier to manage and segregate configuration properties. Storing all properties in a single file or embedding them in the source code is not a scalable or maintainable approach. A centralized configuration service can be complex and less flexible for individual modules.

The @ConditionalOnClass annotation, when used in the context of Auto Configuration, defines a required class for Auto Configuration to be enabled. If the specified class is present on the classpath, the associated configuration will be applied. This allows developers to conditionally configure components based on the availability of certain classes. It does not ignore, disable, or indicate conditional bean creation.

In Spring Boot, the value attribute of the @ExceptionHandler annotation is used to specify the types of exceptions that a particular method should handle. By specifying the exception types, you can ensure that the method is invoked only when those specific exceptions are thrown, allowing for more fine-grained exception handling in your application.

In Mockito, the when method is used to stub a return value for a method call. This allows you to define the behavior of a mocked object when a specific method is called during testing.

In projects with multiple beans and dependencies, @Primary should be used to define a default bean when no qualifier is specified. This provides a clear choice when there is ambiguity. However, it should be used judiciously, especially when there are multiple beans of the same type. It should not be overused, as it can lead to unexpected behavior. The other options do not accurately represent best practices for using @Primary.

In Spring Boot, to customize the storage and retrieval of cache, a developer can implement the CacheResolver interface. This interface provides methods to resolve cache instances dynamically. The other options are not standard interfaces for customizing caching in Spring Boot.

The process of supplying an external dependency to an object in Spring is called "Dependency Injection." It involves injecting or providing the required dependencies to an object rather than having the object create them itself, promoting loose coupling and easier testing.