Answer: The answer choice I will go with is B. Gertude is opening up the possibility that Ophelia did not kill herself.
It should be moved to the beginning of the sentence, that means, that it should be placed before "The motorcycles raced" (option A).
Explanation: "down the track" is a prepositional phrase. All prepositional phrases have no verbs nor subjects. These can be used as adjectives or adverbs. They can be placed either after the verb and at the begining of a sentence. When placed at the beginning of a sentence, it sounds more formal than the common structure composed of 'subject + verb + predicate' and this construction has to be followed by a comma.
In this case, the answer would be:
'Down the track, the motorcycles raced for the prize'.
I would imagine the reader would feel anxious, especially to know what would happen next. It's a turn of events that will leave you on the edge of your seat.
The correct answer is a. Hope that helps!