$9.$ Hydrocracking is primarily used to:

a$)$ Increase the octane rating of gasoline

b$)$ Reduce the sulfur content of diesel

c$)$ Convert heavy hydrocarbons into lighter ones

d$)$ Produce lubricating oils

$10.$ Reforming is a process used to:

a$)$ Increase the cetane number of diesel

b$)$ Improve the color of petroleum products

c$)$ Enhance the octane rating of gasoline

d$)$ Reduce the viscosity of heavy oils

$11.$ Which of the following is not a product of catalytic reforming?

a$)$ Naphtha

b$)$ LPG

c$)$ Butane

d$)$ Aromatics

$12.$ Alkylation is a process used to:

a$)$ Increase the sulfur content of gasoline

b$)$ Enhance the color of petroleum products

c$)$ Improve the antiknock properties of gasoline

d$)$ Reduce the vapor pressure of diesel