Which of the following statements about the multiplex section remote error indication (MS-REI) is correct?

Which of the following statements about the multiplex section remote error indication (MS-REI) is correct?

① The B2 byte indicates the transmission channel.

② The M1 byte indicates the transmission channel.

③ MS-REI is transmitted from the sink to the source.

④ MS-REI is transmitted from the source to the sink.

⑤ Indicates the number of detected bit errors after the sink receives the MS signals.
A . ①④⑤
B . ②④⑤
C . ①③⑤
D . ②③⑤