$35.$ Which of the following is true about Packie charts?

$-$ A$)$ They are used to determine the molecular weight of crude oil fractions.

$-$ B$)$ They help in planning the logistics of crude oil transportation.

$-$ C$)$ They are useful for analyzing distillation column performance and making cut point decisions.

$-$ D$)$ They track the price fluctuations of crude oil in the market.

$36.$ Why is desalting considered a critical first step in the refining process?

$-$ A$)$ It enhances the lubricating properties of the oil.

$-$ B$)$ It prevents catalyst poisoning in subsequent processing steps.

$-$ C$)$ It increases the thermal stability of the oil.

$-$ D$)$ It reduces the overall time needed for refining.

$37.$ Atmospheric distillation is used to separate crude oil based on:

$-$ A$)$ Density gradients

$-$ B$)$ Boiling point differences

$-$ C$)$ Molecular size

$-$ D$)$ Solubility differences

$38.$ The main reason vacuum distillation is used after atmospheric distillation is to:

$-$ A$)$ Increase the API gravity of heavy crude oil.

$-$ B$)$ Further separate heavier fractions that require lower pressure to vaporize.

$-$ C$)$ Remove any remaining water in the crude oil.

$-$ D$)$ Enhance the color of the final petroleum products.