Ans will be 2) pk(R1)→pk(R2)
Consider the following case
A many-to-one relationship set exists between entity sets students and course (a relation r with primary key roll_no )
let it is decomposed in 2 relations r1(student with Pk roll_no ) and r2 (course with Pk course name )
Roll_no can uniquely identify course name but course name can not uniquely identify roll_no
so the functional dependency Pk(student) → Pk(course) indicates a many-to-one relationship between r1 and r2