Answer is A, B, C

Reference: https://help.salesforce.com/s/articleView?id=platform.workflow_field_update_considerations.htm&type=5

A-> If your organization uses multiple currencies, currency fields are updated using the record's currency. If you choose to update a field based on a formula, any values in your formula are interpreted in the currency of the record.

B-> Field updates function independently of field-level security. Therefore, a workflow rule can update fields even though they’re hidden on the user's page layout.

C->Workflow rules and some processes can invalidate previously valid fields. Invalidation occurs because updates to records based on workflow rules and also on process-scheduled actions don’t trigger validation rules.

Ist B, C & D