It must be C bcoz it is the only option in which lossless decomposition condition can be safisfied.
and on joining the two tables..we'll not get any extra row.
For lossless decomposition : from the joining table's....one of the table's column must be key(or we can say unique or distinct).
for example R(a,b,c) and S(x,b,z) are two tables.So,for lossless decomposition the common attribute (i.e., 'b' ) for one of the table must be unique.
select R.* from R,(select distinct a from S) as S1 where R.a=S1.a
Here we are simply making the column 'a' of table 'S' distinct.Therefore satisfying the above condition.
Correct me if I am wrong