herylanne mixes together Chemical A and Chemical B in a test tube, forming Chemical C. The mixture instantly turns cool to the touch. She then adds Chemical D, and the reaction becomes hot and explodes. What can be known about this situation? Chemicals A and B form an endothermic reaction, and chemicals C and D form an exothermic reaction. Chemicals A and B form an exothermic reaction, and chemicals C and D form an endothermic reaction. Chemicals A and C form an endothermic reaction, and chemicals B and D form an exothermic reaction. Chemicals A and B form an exothermic reaction, and chemicals B and D form an endothermic reaction.