$13.$ Which component is typically NOT removed during the desalting process of crude oil?

$-$ A$)$ Water

$-$ B$)$ Salt

$-$ C$)$ Heavy metals

$-$ D$)$ Volatile organic compounds

$14.$ What is the primary purpose of an atmospheric distillation unit in a refinery?

$-$ A$)$ To increase the pressure within the distillation column

$-$ B$)$ To separate crude oil into lighter fractions under atmospheric pressure

$-$ C$)$ To remove all sulfur content from crude oil

$-$ D$)$ To crack heavy hydrocarbons into lighter ones

$15.$ The vacuum distillation unit is primarily used to:

$-$ A$)$ Increase the yield of gasoline

$-$ B$)$ Distill heavier fractions at lower temperatures

$-$ C$)$ Remove nitrogen compounds

$-$ D$)$ Produce petrochemical feedstocks

$16.$ What does the API gravity of crude oil indicate?

$-$ A$)$ The sulfur content

$-$ B$)$ The acidity

$-$ C$)$ The density relative to water

$-$ D$)$ The viscosity