A) She decides to burn the methane gas in O2 (Called Combustion)
B) Because like previous poster mentioned, the activation energy for the reaction to occur is too high, meaning the reaction will take forever, and not occur at all. In other words, too much energy is required; energy that does not increase by adding to concentration.
C) You can use a catalyst to lower the activation energy, or you can raise temperature. (Or lower depending on what reactions you are doing. For the purpose of combustion though, I would say, raise)
She needs activation energy to get the reaction to start eg a light or a spark. Once this happens each individual reaction produces the activation energy for the next in a chain reaction