In five flats, one above the other, live five professionals. The professor has to go up to meet his IAS officer friend.

In five flats, one above the other, live five professionals. The professor has to go up to meet his IAS officer friend. The doctor is equally friendly to all, and has to go up as frequently as go down. The engineer has to go up to meet his MLA friend above whose flat lives the professor's friend.

From the ground floor to the top floor, in what order do the five professionals live?  

(a) Engineer, Professor, Doctor, IAS officer, MLA

(b) Professor, Engineer, Doctor, IAS officer, MLA

(c) IAS officer, Engineer, Doctor, Professor, MLA

(d) Professor, Engineer, Doctor, MLA, IAS office