The essential constituent of each organic molecule is the element ________

Explanation

**Step-by-Step Solution:**

1. **Understanding Organic Molecules**: Organic molecules are primarily defined by the presence of carbon atoms. They are the building blocks of life and are found in all living organisms.

2. **Identifying Essential Elements**: The question asks for the essential constituent of each organic molecule. While organic molecules can contain various elements (like hydrogen, oxygen, nitrogen, etc.), carbon is the fundamental element that characterizes organic compounds.

3. **Definition of Organic Compounds**: Organic compounds are generally defined as compounds that contain carbon. Hydrocarbons, which are compounds made up of carbon and hydrogen, are a primary category of organic compounds.

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