The right answer is A. It requires more coal mining.
In order to manufacture synthetic gasoline, the Fischer-Tropsch process involves the catalysis of carbon monoxide and hydrogen to convert them to hydrocarbon. In this chemical process, the most common catalysts are iron, cobalt or ruthenium, as well as nickel, but the latter will tend to form methane CH4 (this is called methanation). The interest of conversion is to produce synthetic crude oil from coal or gas. This process has a very good yield but requires very heavy investments, which makes it economically vulnerable to downward fluctuations in the price of oil.