The correct syntax to pass a variable from the root module to a child module isservers = var.num_servers.
Terraform uses dot notation to reference variables.
References:
Terraform Variables

Rationale for Correct Answer (B):
The file() function reads a file from disk and returns its content as a string. This is commonly used for public keys (.pub files).
Analysis of Incorrect Options:
A). fileset(): Returns a set of filenames matching a pattern, not file contents.
C). filebase64(): Reads file and returns Base64 encoded string - unnecessary for .pub.
D). templatefile(): Used for rendering templates with variables, not raw file contents.
Key Concept:
Terraform's file() function is used for injecting file content directly.
Reference:Terraform Exam Objective - Read, Generate, and Modify Configurations.

To prevent two Terraform runs from changing the same state file simultaneously, state locking is used. State locking ensures that when one Terraform operation is running, others will be blocked from making changes to the same state, thus preventing conflicts and data corruption. This is achieved by configuring the state backend to support locking, which will lock the state for all operations that could write to the state.References
= This information is supported by Terraform ' s official documentation, which explains the importance of state locking and how it can be configured for different backends to prevent concurrent state modifications .

Detailed Explanation:
* Rationale for Correct Answer: To bring existing infrastructure under Terraform management, Terraform needs both a matching resource block in the configuration and an import declaration or import command that maps the real cloud object to the Terraform resource address. With modern configuration-driven import, you add an import block and a corresponding resource block, then run Terraform to import the object into state.
* Analysis of Incorrect Options (Distractors):
* A. Pick the two correct responses below. Incorrect. This is an instruction, not an action.
* B. Run terraform state pull. Incorrect. This only downloads and displays the current state. It does not import existing cloud resources.
* E. Run terraform apply -refresh-only. Incorrect. Refresh-only updates Terraform state for resources already managed in state. It does not import unmanaged VMs.
* Key Concept: Existing infrastructure must be imported into Terraform state and represented in Terraform configuration before Terraform can manage it.
Reference: Terraform Objective Domain: Use Terraform to Manage Infrastructure

Detailed Explanation:
Rationale for Correct Answer:Terraform import (including the newer import block workflow) needs:
A: the target resource address (e.g., aws_db_instance.main or module.db.aws_db_instance.main) where Terraform should map the existing remote object into state, and C: the provider-specific import ID that uniquely identifies the existing database in the provider (for AWS RDS, Azure, GCP, etc. each has a defined import ID format).These are the two required pieces to tell Terraform what to import and where to place it in state.
Analysis of Incorrect Options (Distractors):
B: Incorrect. Terraform does not require a file path; it loads configuration from the working directory. What matters is the resource address exists in the configuration, not where it is located.
D: Incorrect. Platform/version may be relevant to configuring the resource correctly afterward, but it is not required to create the import mapping.
E: Incorrect. Terraform providers typically authenticate using configured credentials, not a "connection string" for importing. Import IDs are used instead.
Key Concept:Importing existing resources: mapping remote object ID to a Terraform resource address in state.
Reference:Navigate Terraform State and Backends - importing resources into state (terraform import / import blocks), resource addressing, and provider import IDs.