Which of the Following in NOT a Step in Fractional

Which of the following in NOT a step in fractional distillation of crude oil?

A) The crude oil is pumped into a large vessel and heated.
B) As the temperature increases,the compounds vaporize.
C) Fractions are mixed with natural gas to enrich the hydrocarbon content.
D) Once in the gas phase,compounds travel up the tall distillation or fractionation tower.The compounds with smaller molar masses travel higher;the compounds with larger molar masses travel shorter distances up the column