What is the amount of energy called from the reactants to the top of the curve? a. total heat energy
b. catalyst energy
c. decomposition energy
d. activation energy

i believe the answer is a.

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.