TASK DEFINITION: You need to read the given sentence and construct a question about the information present in the sentence. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is unique. The question must involve coreference resolution which is a task of clustering mentions in text that refer to the same underlying real world entities. For example let's take a sentence 'I voted for Obama because he was most aligned with my values, she said.' Here in this example 'I', 'my', and 'she' belong to the same cluster and 'Obama' and 'he' belong to the same cluster. Now let's discuss another example , original sentence: 'I voted for Trump because he was most aligned with my values',John said. Now here is the same sentence with resolved coreferences: 'John voted for Trump because Trump was most aligned with John's values',John said.
PROBLEM: Sentence: As Ollie carried Tommy up the long winding steps, his legs ached.

SOLUTION: Whose legs ached?

PROBLEM: Sentence: The police arrested all of the criminals. They were trying to stop the drug trade in the neighborhood.

SOLUTION: Who was trying to stop the drug trade?

PROBLEM: Sentence: The scientists are studying three species of fish that have recently been found living in the Indian Ocean. They appeared two years ago.

SOLUTION:
Who or what appeared two years ago?