The sentence discusses Sue's current whereabouts. Thus, the answer must be in present tense. Also, it should fit well with 'late'.
Option A is incorrect. Got is past tense. Since the sentence is in present tense, got cannot be correct.
Option B is incorrect. Happen does not fit well with late and also makes the sentence grammatically incorrect.
Option C is correct. Be is in present tense and also fits well with late. 'not to be late' makes perfect sense and thus it is the correct option.
Option D is incorrect. Although, go is in present tense and also fits in the blank, it is not a good fit. Be is a much better fit than go in this sentence.