सीवेज का द्वितीयक उपचार (secondary treatment) मुख्य रूप से निम्नलिखित में से किसके कारण होता है?

In a typical untreated domestic sewage wastewater sample, which of the following is expected to have the highest concentration value (mg/L)?

Arrange the following greenhouse gases in increasing order of their overall relative contribution to global warming (percentage share): A. CO2 B. N2O C. CFCs D. CH4