The correct option is Stmt. In Go's database/sql package, the Stmt interface represents a prepared statement. Prepared statements allow you to execute the same SQL statement repeatedly with high efficiency.

The HTTP header commonly used for transmitting authentication credentials is "Authorization". This header carries the credentials needed to authenticate the client's request to the server.

In Go, you can ensure that all test files are executed when running unit tests by using the go test ./... command. This command recursively tests all packages and subpackages within the current directory. Specifying all test files explicitly when running go test may be cumbersome and error-prone, especially in projects with numerous test files. The go test -run all command doesn't exist in Go and wouldn't serve this purpose. Ensuring that each test file imports the main package wouldn't guarantee that all test files are executed, as some may not have test functions. Therefore, using go test ./... is the recommended approach to test all files in a package.

In Go programming, ORM stands for Object-Relational Mapper. ORM is a technique to map objects from an application to tables in a relational database. It simplifies the database interaction by abstracting the SQL queries into higher-level programming constructs.

In Go, arrays have a fixed size that cannot be changed, whereas slices are dynamically resizable. This means you can append or remove elements from a slice, but not from an array. Arrays are passed by value, while slices are passed by reference.

The correct function to create a new slice by slicing an existing slice or array is append(). This function appends elements to a slice, effectively creating a new slice containing the appended elements.

The 'testing' package in Go provides support for writing tests and benchmarks. Benchmarks are written using the 'Benchmark' function provided by this package. This function allows developers to measure the performance of their code under different scenarios and inputs, providing valuable insights into the efficiency of their implementations.

In Go, the performance complexity of map operations, such as insertion, deletion, and lookup, is typically O(1) on average. This means that these operations have constant time complexity, irrespective of the size of the map. Go's map implementation utilizes a hash table data structure internally, which allows for efficient retrieval and manipulation of key-value pairs. Understanding the performance characteristics of maps is essential for writing efficient Go code, especially when dealing with large datasets or performance-critical applications.

Using mutexes is a common way to ensure safe access to shared data in Go. Mutexes provide exclusive access to the shared resource, allowing only one goroutine to access it at a time. By locking and unlocking the mutex appropriately, you can prevent race conditions and ensure data integrity.

The for loop in Go is typically used when the number of iterations is known. It provides a concise syntax for iteration and is commonly used in Go code.