In decipher jumbled up description type of questions, a round-about description is given in the form of certain small relationships and direct relationship between the persons concerned is to be deciphered.
Pointing out to a lady, Rajan said, "She is the daughter of the woman who is the mother of the husband of my mother."
Who is the lady to Rajan ?
The relations may be analysed as follows :
Mother's husband -- Father;
Father's mother -- Grandmother;
Grandmother's daughter -- Father's sister;
Father's sister -- Aunt.
So, the lady is Rajan's aunt.
Hence, the answer is (a).