The major product `(X)` of the reaction
`CH_(3)CH_(2)NH_(2)+HCHO+HCOOHoverset(Delta)rarrX` is .

Options

A. `(CH_(3)CH_(2))_(2)NH`
B. `(CH_(3))_(2)NH`
C. `CH_(3)CH`
D. A mixture of all the

Explanation

To determine the major product \( X \) of the reaction between ethylamine \((CH_3CH_2NH_2)\), formaldehyde \((HCHO)\), and formic acid \((HCOOH)\) upon heating, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Reactants**: The reactants are ethylamine, formaldehyde, and formic acid. Ethylamine is a primary amine.

2. **Understand the Reaction Type**: The reaction involves a primary amine reacting with formaldehyde and formic acid. This is a type of methylation reaction where the amine is converted to a secondary amine.

3. **Methylation Process**: In this reaction, the primary amine (ethylamine) will react with formaldehyde to form an N-methylated product. The hydrogen atom from the amine group will be replaced by a methyl group from formaldehyde.

4. **Formation of the Product**: The reaction can be summarized as follows:
- Ethylamine \((CH_3CH_2NH_2)\) reacts with formaldehyde \((HCHO)\) to form N-methyl-ethylamine \((CH_3CH_2NHCH_3)\).
- The formic acid can help stabilize the intermediate formed during the reaction.

5. **Final Structure of Product \( X \)**: The major product \( X \) after the reaction is N-methyl-ethylamine, which has the structure:
\[ CH_3CH_2NHCH_3 \]

### Conclusion:
The major product \( X \) of the reaction is N-methyl-ethylamine, represented as \( CH_3CH_2NHCH_3 \).