下面哪种单板不适合用于集团专线大颗粒业务接入（）

A.CX21
B.CX31
C.CX51
D.CX71

A.传输子架transmission sub-rack
B.CX20子架\nCX20 sub-rack
C.CX子架\nCX sub-rack
D.CX30子架\nCX30 sub-rack

A.NX41
B.DX41
C.NX4
D.CX71