How can these six shapes be classified?
a.
trapezoid
b.
parallelogram
c.
not a trapezoid or parallelogram

Ibelieve the answer is c

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen

Answeroil-shale;