Question

fundamental rights and duties are complementary to each other

Answer 1

Yeah, the statement sounds pretty much true.
What is the use of having some rights, which you don't know,where to apply.Duties, shows your obligations to complete or undertake tasks,and if you face some sort of challanges in fulfilling your obligations,don't you think then only will the fundamental rights be of any use to you.
Hope that is of some help. :)