Error spotting (question word choice): Identify the erroneous segment (A/B/C) — mark D if there is no error — 'What does Professor Dhavan / spend so many hours / in the laboratory? / No error.' Check idiomatic interrogatives.

Given data

• (A) What does Professor Dhavan
• (B) spend so many hours
• (C) in the laboratory?

Concept/Approach: Appropriate wh-word
We ask for a reason with 'why', not 'what': 'Why does Professor Dhavan spend so many hours…?' Alternatively, if 'what' is retained, the verb needs an object ('What does … spend hours on in the laboratory?'), which is absent here.

Step-by-step correction
Preferred: 'Why does Professor Dhavan spend so many hours in the laboratory?'Alternative (object question): 'What does Professor Dhavan spend so many hours on in the laboratory?'

Common pitfalls
Using 'what' to seek reasons; omitting required prepositions.

Final Answer
A — Replace 'What' with 'Why' (or supply the missing object/preposition).