Bibliography is essential in determining its content. I hope this helped
Coal came from swampy environments, while oil and natural gas came from open ocean environments is true about fossil fuels. The correct option among all the options that are given in the question is the third option or option "c". Coal mainly came from decomposition of plants for a long time and oils as well as natural gases are mostly found in ocean environments.
A control group is important to a controlled experiment because it is used in an experiment to establish its validity.
An example of secondary pollutant is sulfurage