💡 Detailed Explanation
The phrase '～であろうと' is equivalent to 'たとえ～であっても' and expresses a hypothetical counter-condition, meaning 'even if' or 'no matter how'. 'どんなに困難であろうと' means 'no matter how difficult the situation may be,' which logically connects to the strong will expressed in the latter part of the sentence: 'I want to see it through to the end.' The other options are grammatically or semantically inappropriate.