The correct option is A C
The given sentence talks about the unusually late arrival of a train. In part [C] of the sentence, we see the article 'a' being used before the word 'hour', which is incorrect. According to English grammar, 'hour' is pronounced with a silent 'h' and such words are preceded by article 'an' just like vowels are. Therefore, the incorrect part of the given sentence is part [C] and the correct answer is option (C).