The correct option is C Mike is so ill that the doctors suspect he may not survive.
A conjunction combines or connects two sentences as one. They can either be a word or a phrase (like even if, as well as, etc). Correlative conjunctions are words in pairs that connect two sentences, but they're not written together, for example, either...or, but...and, such...that etc, where there's a word/s in between the pair. 'So that' and 'so...that' have different meanings. 'So that' refers to purpose, it expresses the reason for which an action is carried out, as in 'I left early so that I could attend the party'. The given sentence does not focus on purpose, but the result, where 'so' emphasizes a quality or condition, here it emphasizes "ill", and "that" brings out the result "doctors suspect he may not survive". This can be seen in option C, which is correct. In option A, 'so that' refers to purpose, it sounds as if the purpose for Mike being ill was that the doctors suspect he might not survive, which sounds illogical, hence option A is incorrect. In B, the sentence sounds a little off, because 'that' has been placed between the result, but the result should include the doctors' suspecting, 'that' should be placed right after "ill", as it refers to the effect that follows, hence option B is incorrect. In option D, the correlatives 'so...that' have been interchanged in order, 'that' has been used in place of 'so' and vice versa. The sentence does not have a proper meaning, 'that' in this sentence acts as a demonstrative, and the order isn't correct, hence option D is incorrect.