In order to transform a conceptual data model to a relational logical data model, for every $M-M$ relationship you see in a conceptual data model, you need to add

PK of one table $($Table A$)$ to the other table $($Table B$)$ as FK and also add PK of Table B to Table A as FK$.$

Add a new table between the two tables $($Table A and Table B$)$ and add PK of Table and PK of Table B to the new table as FKs$.$

Add a new table between the two tables $($Table A and Table B$)$ and add PK of Table and PK of Table B to the new table as FKs and then declare the combination of the two FKs added to the new table as Composite PK of the new table

nothing