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?

Here's a step-by-step deduction:

1. Doctor's position: "The doctor is equally friendly to all, and has to go up as frequently as go down." This implies the Doctor lives in the middle flat. In a 5-flat building, the middle flat is the 3rd flat. Order so far: _, _, Doctor, _, _

2. Professor and IAS officer: "The professor has to go up to meet his IAS officer friend." This means the Professor lives below the IAS officer (P < IAS).

3. Engineer, MLA, and IAS officer: "The engineer has to go up to meet his MLA friend above whose flat lives the professor's friend."

   • "The engineer has to go up to meet his MLA friend": Engineer lives below MLA (E < MLA).
   • "above whose flat lives the professor's friend": "Whose" refers to the MLA. "Professor's friend" is the IAS officer. This means the IAS officer lives above the MLA's flat (MLA < IAS).

4. Combining the relationships: From E < MLA and MLA < IAS, we get the sequence E < MLA < IAS. We also have P < IAS.

5. Placing the professionals:

   • Doctor is at flat 3.

   • From E < MLA < IAS, and with Doctor at 3, the only way to arrange these three in ascending order is for IAS to be at flat 5 and MLA at flat 4. (IAS must be the highest among them, and MLA below IAS). Order so far: _, _, Doctor, MLA, IAS officer. (Flats 1, 2, 3, 4, 5)

   • Now, Engineer (E) and Professor (P) are left for flats 1 and 2.

   • We need to satisfy P < IAS (P < 5) and E < MLA (E < 4).

   • If Professor is at flat 1 and Engineer is at flat 2: Order: Professor, Engineer, Doctor, MLA, IAS officer. (Flats: 1, 2, 3, 4, 5) Let's check the conditions:

     • P < IAS (1 < 5): Yes.
     • E < MLA (2 < 4): Yes.
     • MLA < IAS (4 < 5): Yes.
     • Doctor is at 3: Yes. This order satisfies all conditions.

This order matches Option D.

The final order from ground floor to top floor is: Professor, Engineer, Doctor, MLA, IAS officer.

The final answer is D