$17.$ Which of the following is a common application of ethylene?

a$)$ Production of pharmaceuticals

b$)$ Manufacturing of paints and coatings

c$)$ Fuel for industrial boilers

d$)$ None of the above

$18.$ What is the primary function of butylene in petrochemical processes?

a$)$ Production of synthetic fibers

b$)$ Manufacturing of detergents

c$)$ Fuel for rockets

d$)$ None of the above

$19.$ Which of the following is NOT a method for producing petrochemical precursors?

a$)$ Steam cracking

b$)$ Catalytic reforming

c$)$ Hydrogenation

d$)$ Solar distillation

$20.$ Which of the following is a characteristic of petrochemical products?

a$)$ Biodegradable

b$)$ Renewable

c$)$ Derived from fossil fuels

d$)$ Non$-$toxic