Refer to the code snippet below:

As part of an Integration development effort, a developer is tasked to create an Apex method mat solely relies on the use of foreign identifiers In order to relate new contact records to existing Accounts in Salesforce. The account object contains a field marked as an external ID, the API Name of this field is Legacy_Id_c.
What Is the most efficient way to instantiate the parentAccount: variable on line 02 to ensure the newly created contact is properly related to the Account?
A)

B)

C)

D)