$42.$ Which statements regarding the PDU $($Protocol Data Unit$)$ at each layer of the OSI $($Open Systems Interconnection$)$ model is INCORRECT $($More than one statement applies$)?$a$.$The PDU for the Application, Presentation, and Session layers is data.b$.$The PDU at the Transport layer is a packet.c$.$The PDU at the Network layer is a segment.d$.$The PDU at the Data Link layer is a frame.e$.$The final PDU is in the form of bits at the Physical layer.