Well, for the global warming questions (how CO2 causes Earth to heat up) I always say this:
-The Sun emits high-energy UV radiation, warming the Earth
-Earth absorbs UV and emits IR
-IR is absorbed by CO2 molecules, causing their bonds to vibrate more
-This vibrational energy is transferred to kinetic energy
-Energy is re-emitted in all directions causing a rise in atmospheric temp
-A higher conc. of CO2 mean more IR is absorbed so more kinetic energy, so greater heating effect on the Earth
This has always scored me full marks on those questions. The ones about CFCs are different though, do not say the above for those questions.