Does the owner have the right to reject a general contractor's subcontractor who is reasonably capable of performing work?

No$,$ if he passes the threshold of "reasonably capable."

Yes, but the contractor and subcontractor maintain the right to appeal the decision to the architect.

Yes, but the owner will be required to pay any additional costs that may result.

No$,$ the general contractor is the ultimate arbiter of all subcontracts.