Explanation:

Correct Answer is (d).Matter is incorrect as it does not really convey the correct meaning. Matter refers to an issue while here the sentence talks about the consequence of falling oil prices.
Conclude is correct in terms of meaning but incorrect grammatically.
Decision is incorrect as it was not the decision of the government but a set of external factors which led to the drop in oil prices.
Initiation means start/beginning and is incorrect.
Result fits in well contextually and grammatically.
Hence, option D is correct.