Explanation
None of the above methods prevent credentials from being stored in the state file. Terraform stores the provider configuration in the state file, which may include sensitive information such as credentials. This is a potential security risk and should be avoided if possible. To prevent credentials from being stored in the state file, you can use one of the following methods:
Use environment variables to pass credentials to the provider. This way, the credentials are not part of the provider configuration and are not stored in the state file. However, this method may not work for some providers that require credentials to be set in the provider block.
Use dynamic credentials to authenticate with your cloud provider. This way, Terraform Cloud or Enterprise will request temporary credentials from your cloud provider for each run and use them to provision your resources. The credentials are not stored in the state file and are revoked after the run is completed. This method is supported for AWS, Google Cloud Platform, Azure, and Vault. References : [Sensitive Values in State] : Authenticate providers with dynamic credentials

The required_providers block is used to specify the provider versions that the configuration can work with.
The version argument accepts a version constraint string, which must be enclosed in double quotes. The version constraint string can use operators such as >=, ~>, =, etc. to specify the minimum, maximum, or exact version of the provider. For example, version = ">= 3.1" means that the configuration can work with any provider version that is 3.1 or higher. References = [Provider Requirements] and [Version Constraints]

The two steps that are required to provision new infrastructure in the Terraform workflow are init and apply.
The terraform init command initializes a working directory containingTerraform configuration files. It downloads and installs the provider plugins that are needed for the configuration, and prepares the backend for storing the state. The terraform apply command applies the changes required to reach the desired state of the configuration, as described by the resource definitions in the configuration files. It shows a plan of the proposed changes and asks for confirmation before making any changes to the infrastructure. References =
[The Core Terraform Workflow], [Initialize a Terraform working directory with init], [Apply Terraform Configuration with apply]

The key principle of infrastructure as code that is not listed among the options is golden images. Golden images are pre-configured, ready-to-use virtual machine images that contain a specific set of software and configuration. They are often used to create multiple identical instances of the same environment, such as for testing or production. However, golden images are not a principle of infrastructure as code, but rather a technique that can be used with or without infrastructure as code. The other options are all key principles of infrastructure as code, as explained below:
Self-describing infrastructure: This means that the infrastructure is defined in code that describes its desired state, rather than in scripts that describe the steps to create it. This makes the infrastructure easier to understand, maintain, and reproduce.
Idempotence: This means that applying the same infrastructure code multiple times will always result in the same state, regardless of the initial state. This makes the infrastructure consistent and predictable, and avoids errors or conflicts caused by repeated actions.
References = [Introduction to Infrastructure as Code with Terraform], [Infrastructure as Code in a Private or Public Cloud]

This is a bad practice, as it exposes your credentials to anyone who can access your configuration files or state files. You should use environment variables, credential files, or other mechanisms to provide credentials to Terraform.