Let pk(R) denotes primary key of relation R. A many-to-one relationship that exists between two relations R1 and R2 can be expressed as follows :

A.

pk(R2) → pk(R1)

pk(R1) → pk(R2)

C

pk(R2) → R1 ∩ R2

pk(R1) → R1 ∩ R2

check this https://gateoverflow.in/225331/ugc-net-july-2018-q67