Certainly! The question as shown in the image is:

"When we have a one$-$to$-$one relationship, with one optional and one mandatory minimum cardinality, PK of which entity should be FK in another entity?"

And the options given below are:

A$.$ The PK of BILL will be the FK in TRANSACTION.

B$.$ The PK of TRANSACTION will be the FK in BILL.

C$.$ The PK of BILL will be the FK in TRANSACTION, and The PK of TRANSACTION will be the FK in BILL.

D$.$ B and C

Given that TRANSACTION is the mandatory entity and BILL is the optional entity in a one$-$to$-$one relationship, the PK of the optional entity $($BILL$)$ should be the FK in the mandatory entity $($TRANSACTION$).$ So$,$ the first option $($A$)$ is the correct one.