Please help What rock layer marks the end of the dinosaurs?

Question 1 options:

Burgess Shale layer

Mesozoic Layer

KT Boundary layer

Which best describes the activation energy of a chemical reaction? a. the combined energy of all the reactants b. the amount of energy required for a reaction to occur c. the difference in energy between products and reactants d. the potential energy stored in the bonds of reactants and products