ramarao443 Normally we don't switch antecedents for a pronoun. In other words, once we've said that "it=disease," we don't assign "it" or "its" to any other noun. With this in mind, A would seem problematic. However, there are a few complications:
*First, there has been no possessive noun except for "parasite's." We aren't supposed to use a possessive pronoun unless there's an actual possessive noun to refer back to, so this points toward "parasite's"
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*First, there has been no possessive noun except for "parasite's." We aren't supposed to use a possessive pronoun unless there's an actual possessive noun to refer back to, so this points toward "parasite's"
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