Ans is option a)
Let R be the relational schema with instance r is decomposed into R1,R2,….,Rn with instance r1,r2,…..,rn.
If r1 ⋈ r2 ⋈ ……. ⋈ rn ⊃ r , then it is called Lossy Join Decomposition.
i.e. if the original relation is the proper subset of natural joins of all the decompositions, then it is said to be Lossy Join Decomposition.