The correct pairing of a greenhouse gas with its primary anthropogenic source is: Methane and vehicular emissions.
The Greenhouse Effect is a naturally occurring process that is necessary for the maintenance of the planet's temperature. The sun's energy travels to Earth in the form of light. The Earth reflects some of this energy back to space while absorbing the remainder, which warms the planet.
Methane is a greenhouse gas that is released by several human activities, including fossil fuel production and use, landfills, agriculture, and livestock farming. Methane, like carbon dioxide, contributes to global warming by trapping heat in the Earth's atmosphere.
Vehicular emissions are the gases and particulate matter emitted by vehicles. They include carbon monoxide, nitrogen oxides, particulate matter, and other pollutants that are hazardous to human health and the environment.