Concept:This sentence tests the third conditional, which talks about an unreal past condition and its imagined result.
Explanation:The correct structure is: If + past perfect, would have + past participle.
Part A: “If I had left the compartment” is correct.
Part B: “and gone out to fetch drinking water” is correct.
Part C: “I had lost my luggage” is wrong.
It should be “I would have lost my luggage and other belongings.”
So the error is in part C.
Answer:The error is in part (C).