About bidirectional 1:1 T-MPLS path protection, which of the following are correct? ()

A. In 1:1 mode, protection connection is specific to each work connection; the protected work service is transmitted by work or protection connection.

B.Whether work connection or protection connection is selected depends on some certain type of mechanism. To avoid single point failure, work connection and protection connection should take separate routes.

C.During the switching, APS is needed for negotiating two sides of the connection. Bidirectional 1:1 T-MPLS path protection should be revertive type.

D.1：1 T-MPLS path protection is bidirectional switching type. That is to say, connections in both affected or non-affected directions are switched to protection paths.