An architect has a requirement to create a criteria-based sharing rule based on the customer...

Field-Level Encryption and Sharing Rules:

When a field is encrypted using Salesforce Shield Platform Encryption, it is not available for sharing rules or criteria-based sharing because the encrypted field value is inaccessible for evaluations.

Why Option A is Correct:

The Social Security Number field is likely encrypted, which prevents it from being available in the sharing rule criteria.

Why Others Are Incorrect:

Option B: Field Level Security (FLS) affects visibility for the architect but does not determine availability in sharing rules.

Option C: Compliance fields are not a concept related to this issue.

For further reference, see Salesforce Shield Platform Encryption documentation: https://help.salesforce.com/