Answer:
D. While walking to the park today, I saw a house burst into flames.
Step-by-step explanation:
In sentence A: I saw a house on fire walking to the park today, it gives off the impression, that the house itself was walking to the park, whilst in fact on fire. In sentence B: Walking to the park today, a house burst into flames, this sentence can go both ways. Some people may be able to interpret this correctly, but in other words, this sentence has an incorrect subject change, throwing the whole sentence off course. And in sentence C: Today while walking to the park, a house was on fire, this sentence delivers the same format as sentence A. Sentence D, is the only sentence with correct punctuation, in the correct places, and the only sentence that has the correct subject and direct object agreement.