Infact,most nahptha is produced from crude oil in the first step of the refining process distillation (Speight,2014,2017) light nahptha is composed predominantly of pentane and hexane derivatives as well as smaller amounts of higher molecular weight hydrocarbon derivatives.

Crude naphtha is a complex mixture of hydrocarbons that is obtained during the distillation of crude oil. It is primarily composed of alkanes, hence the correct answer is option 'A'.

Here is a detailed explanation of why crude naphtha is mainly composed of alkanes:

1. Composition of Crude Oil:
Crude oil is a mixture of various hydrocarbons, including alkanes, cycloalkanes, aromatic hydrocarbons, and small amounts of other compounds such as sulfur, nitrogen, and oxygen-containing compounds. The composition of crude oil varies depending on the source, and it can be further separated into different fractions based on boiling points.

2. Distillation Process:
Crude oil is subjected to fractional distillation to separate it into different fractions based on boiling points. During this process, the crude oil is heated, and the vapors are passed through a fractionating column, where the separation takes place. The different fractions obtained include gases, gasoline, diesel, kerosene, and residual fuel oil.

3. Naphtha Fraction:
Naphtha is one of the fractions obtained during the distillation process. It has a boiling point range between gasoline and kerosene. Naphtha is further categorized into light naphtha and heavy naphtha, depending on their boiling points.

4. Alkane Dominance:
Crude naphtha, which is the focus of this question, is primarily composed of alkanes. Alkanes are saturated hydrocarbons that contain only single bonds between carbon atoms. They have a general formula of CnH2n+2, where "n" represents the number of carbon atoms. Alkanes are the most abundant and stable hydrocarbons found in crude oil.

5. Other Components:
Although alkanes are the main constituents of crude naphtha, it may also contain small amounts of other hydrocarbons such as cycloalkanes and aromatic hydrocarbons. However, these components are present in lesser quantities compared to alkanes.

Conclusion:
In conclusion, crude naphtha is primarily composed of alkanes, making option 'A' the correct answer. Alkanes are the most abundant and stable hydrocarbons found in crude oil. The composition of crude oil may vary depending on the source, but alkanes are the dominant components in the naphtha fraction obtained during the distillation process.