For each Primary key, you need a foreign key field in the related table:
A::A1 = B::A1Match
B::B1 = C::B1Match
A1, B1, C1 should be either number fields that auto-enter a serial number or text fields that auto-enter Get ( UUID ). The foreign key fields, which I've named with "match" as part of the field name here, would be simple data fields of the same data type as the corresponding Primary Key.