$9.$ Vacuum distillation in crude oil processing is applied because:

$-$ A$)$ It increases the boiling point of the fractions

$-$ B$)$ It decreases the boiling point of heavier fractions

$-$ C$)$ It is a more energy$-$efficient process

$-$ D$)$ It removes all the impurities

$10.$ The degree of separation $(5-95$ gap$)$ refers to:

$-$ A$)$ The temperature difference between $5\%$ and $95\%$ recovered volumes in distillation

$-$ B$)$ The sulfur content gap

$-$ C$)$ The API gravity difference

$-$ D$)$ The viscosity range

$11.$ The degree of difficulty of separation $($t $50)$ is:

$-$ A$)$ The temperature difference needed to separate middle $50\%$ of a mixture

$-$ B$)$ A measure of sulfur content difficulty

$-$ C$)$ Related to the acidity of the crude

$-$ D$)$ The gap between API gravities of fractions

$12.$ Packie charts are used to:

$-$ A$)$ Classify crude oil based on sulfur content

$-$ B$)$ Plot distillation curves for petroleum fractions

$-$ C$)$ Measure the density of crude oil

$-$ D$)$ Determine the viscosity of crude oil