$13.$ Polymerization involves the:

a$)$ Breaking down of large hydrocarbons into smaller ones

b$)$ Combining of small hydrocarbon molecules into larger ones

c$)$ Conversion of alkenes into alkanes

d$)$ Separation of aromatics from other hydrocarbons

$14.$ Isomerization is a process used to:

a$)$ Increase the octane number of gasoline

b$)$ Decrease the flash point of diesel

c$)$ Improve the lubricating properties of oil

d$)$ Reduce the vapor pressure of kerosene

$15.$ Which of the following is not a petroleum product?

a$)$ Ethanol

b$)$ Naphtha

c$)$ Gasoline

d$)$ Lubricants

$16.$ Motor gasoline primarily consists of:

a$)$ C$7-$C$10$ hydrocarbons

b$)$ C$5-$C$8$ hydrocarbons

c$)$ C$9-$C$12$ hydrocarbons

d$)$ C$6-$C$9$ hydrocarbons