Basically, the graph shows a linear (line) relationship with mass and volume. The slope will equal the density of the substance because mass/volume is the equation for density. Your paper is a bit unclear, but I can understand this much, Hope this helped a little bit :)
A species with a positive charge will have a net attraction to a species with a negative charge. Among the choices, N3- is the only one attracted to a positive charge.
The correct answer is carbon dioxide and water vapor
These negative gasses get modified and then remain in the atmosphere without the possibility of leaving, which is why the greenhouse effect occurs.
