TASK DEFINITION: In this task, you're given a sentence and question. Based on the information provided in a given sentence, you should identify the shortest continuous text span from the sentence that serves as an answer to the given question. Answer the question using coreference resolution. Coreference resolution is the 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. Question: Whose legs ached?

SOLUTION: Ollie

PROBLEM: Sentence: The journalists interviewed the stars of the new movie. They were very cooperative, so the interview lasted for a long time. Question: Who was cooperative?

SOLUTION: stars

PROBLEM: Sentence: Kirilov ceded the presidency to Shatov because he was more popular. Question: Who was more popular?

SOLUTION:
Shatov