What is the basic unit of framing in SDH and the bit rate for transmission? 

STM-1 with a bit rate of 1.544 Mbit/s. 

STM-1 with a bit rate of 2.048 Mbit/s. 

STM-1 with a bit rate of 51.84 Mbit/s. 

STM-1 with a bit rate of 155.52 Mbit/s.