The process through which crude oil is separated into useful substances is called __________of petroleum.

Options

A. refining
B. fractioning
C. distillation
D. None of them

Answer

To answer the question, we need to identify the process through which crude oil is separated into useful substances.

### Step-by-Step Solution:

1. **Understanding Crude Oil**: Crude oil is a natural, unrefined petroleum product composed of hydrocarbon deposits and other organic materials.

2. **Separation Process**: The separation of crude oil into various useful substances involves a specific process that allows different components to be extracted based on their boiling points.

3. **Identifying the Correct Term**: The process through which crude oil is separated into useful substances is known as "refining". This process includes various techniques such as distillation, which separates the crude oil into fractions.

4. **Final Answer**: Therefore, the correct term to fill in the blank is "refining".

### Complete Answer:
The process through which crude oil is separated into useful substances is called **refining** of petroleum.

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