The correct answer in here is: Limited the burning of soft coal. Some reasons for that are that when Britain was the workshop of the world its coal consumption increased from around 10 million tons per annum in 1800 to almost 200 million tons in 1950 and also that Coal smoke was linked to very high death rates from respiratory diseases such as bronchitis, killing between 800,000 and 1.4 million people in the period 1840-1900.
