In this task you need to give reasons to justify the pronoun coreference relations. Each of the provided inputs contains a sentence with a target pronoun and a question about how to justify the coreference between a noun phrase and the target pronoun. Good practices involve the discussion about how the descriptions attached to the targeted pronoun relate to the noun phrase candidate in the question. The reasoning could come from one or multiple following knowledge types about commonsense: First: 'Property', the knowledge about property of objects (e.g., ice is cold). Second: 'Object', the knowledge about objects (e.g., cats have ears). Third: 'Eventuality', the knowledge about eventuality (e.g., 'wake up' happens before 'open eyes'). Forth: 'Spatial', the knowledge about spatial position (e.g., object at the back can be blocked). Fifth: 'Quantity', the knowledge about numbers (e.g., 2 is smaller than 10). Sixth: all other knowledge if above ones are not suitable. Write the sentence in natural language.

Sentence: John hired Bill to take care of him .
 Question: Why does the 'him' refer to john?
Because John cannot hire himself to take care of himself.

Sentence: Sid explained his theory to Mark but he couldn't understand him.
 Question: Why does the 'he' refer to mark?
Because he couldn't understand him.Sid explained his theory to Mar.

Sentence: Sid explained his theory to Mark but he couldn't understand him.
 Question: Why does the 'he' refer to mark?

Because he couldn't understand him.Sid explained his theory to Mar.