Step-by-step explanation:
277 parts per MILLION in 1750 to 422 parts per MILLION today
(422-277) / 277 * 100% = 52% increase ( or 145 parts per million)
I am not sure which answer they want you to pick.....I used historical data....it depends on what year the question was written.....but I think 65% is too high....I would go with answer C