Formaldehyde on treatment with_____gives an_______and salt of a carboxylic and this reaction is called_____.

Explanation

**Step-by-Step Solution:**

1. **Identify the Reactant:**
The question starts with "Formaldehyde." Formaldehyde is the simplest aldehyde with the formula CH₂O.

2. **Identify the Treatment:**
The question asks what formaldehyde is treated with. In the context of the reaction described, formaldehyde is treated with a concentrated base, typically sodium hydroxide (NaOH).

...