While transforming a supertype$/$subtype hierarchy $($in the E$/$R diagram$)$ to a relational structure, the primary key $($PK$)$ of the subtables $($i$.$e$.,$ the tables that correspond to the subentities$)$ will typically

be exactly same as that of the supertable $($i$.$e$.,$ the table that corresponds to the super$-$entity$).$

be a composite key which includes the PK of the supertable as a foreign key

be a simple key but different from that of the supertable.

be a composite key but will not include the PK of the supertable as a FK$.$