Detailed Explanation:

Rationale for Correct Answer: Terraform requires provider aliases when you configure the same provider multiple times in one configuration. You must define the second AWS provider with an alias, then explicitly tell the resource to use it with the provider meta-argument:

provider " aws " {

region = " us-east-1 "

}

provider " aws " {

alias = " west "

region = " us-west-2 "

}

resource " aws_instance " " example_us_west_2 " {

provider = aws.west

ami = data.aws_ami.ubuntu.id

instance_type = " t3.micro "

}

This is a core Terraform objective: selecting the correct provider configuration for a resource when multiple instances exist.

Analysis of Incorrect Options (Distractors):

B: Incorrect. Provider blocks do not support the syntax provider " aws " " west " { ... }. Aliasing is done with alias = " west " .

C: Incorrect. You cannot invent a new provider type name like aws_west. The provider remains aws; you differentiate configurations via alias.

D: Incorrect. Terraform will not automatically choose between multiple provider configurations for the same provider; you must disambiguate using aliases and provider = ....

Key Concept: Provider aliases and the provider meta-argument for multi-region (or multi-account) deployments.