8. Which one is true: There are no units which have volumetric destruction. Hydrogen addition units achieve much higher volumetric conversion than carbon rejection. Both hydrogenation and cracking achieve considerable volumetric expansion. Only Hydrogen addition units achieve volumetric expansion. 9. Adding hydrogen to the feedstock of a carbon rejection unit increases carbon rejection conversion and operating cost. increases conversion and decreases catalyst cost. decreases both conversion and catalyst cost. It has no impact in conversion or operating costs. 10. Which one of the following is true : Refineries always operate at maximum CDU available capacity. Refineries will maximize always refinery conversion capacity. Conversion and CDU units always run at maximum capacity. Most of refineries don't maximize conversion capacity. 11. Which one is true: Topping refineries are more economical than hydro-skimming refineries. Conversion refineries don't make money. Hydro-skimming refineries are less economical than topping refineries. Topping refinery are almost all times uneconomical