C1
In sequence A, the presence of field 21 depends on the value of field 22A as follows (Error code(s): D02):
C2
In sequence C, if field 56a is not present, then field 86a in sequence C is not allowed, otherwise field 86a is optional (Error code(s): E35).
C3
In sequence B, if field 30V is present, then field 38D in sequence B is mandatory, otherwise field 38D is not allowed (Error code(s): D60).
In other words, in sequence B, fields 30V and 38D must either be both present or both absent, and together form the optional subsequence B1 called AFB and FRABBA Details.