💡 Detailed Explanation
The structure '〜なきゃいけない' (nakya ikenai) is a highly common spoken contraction of '〜なければいけない', translating to 'must do...' or 'have to do...'. It connects to the negative form of verbs (dropping 'ない'). It represents everyday obligations and is universally chosen in conversational contexts over the formal '〜なければならない'. In this sentence, it translates perfectly as: "I have to wake up early tomorrow.". The correct option 'いけない' dynamically matches the structural requirements and logical flow of the statement. The other options do not satisfy the grammatical construction or fail to convey the appropriate semantic nuance.