$1.$ The classification of crude oil is primarily based on its $\_\_\_\_,\_\_\_\_$ content, and $\_\_\_\_,$ which affect its refining process and market value.

$2.$ In the desalting process of crude oil, water is used to remove $\_\_\_\_,\_\_\_\_,$ and other impurities before the oil undergoes further $\_\_\_\_.$

$3.$ Crude oil stabilization aims to remove $\_\_\_\_$ components, such as $\_\_\_\_$ and $\_\_\_\_,$ to prevent issues during storage and transportation.

$4.$ Fractional distillation separates crude oil into various fractions based on differences in $\_\_\_\_,$ leading to products like $\_\_\_\_$ and $\_\_\_\_.$