Given the task definition and input, reply with output. You are given a sentence and a question, construct 2 answer options in a specific format i.e. ['option1','option2']. The answer options have to be text spans from the given sentence. Only one among the options should be the correct answer to the given question. Note that, the correct answer to the given question will require understanding of coreference resolution. Coreference resolution is the task of clustering mentions in text that refer to the same underlying real world entities.

Sentence: The scientists are studying three species of fish that have recently been found living in the Indian Ocean. They began two years ago. Question: Who or what began two years ago?

['fish', 'scientists']