Fill in the blank by choosing the appropriate word/words from those given in the brackets.
(acetaldehyde, formaldehyde, benzaldehyde, yellow, white, violet, Cannizzaro's, Liebermann, no `alpha`-hydrogen atom, `1alpha`-hydrogen atom, `2alpha`-hydrogen atoms, aldol, `beta`-hydroxy aldehyde, aldol condensation, mixed condensation, + I,-I, -M,+ M. decreases, increases, benzalchloride, PCI, SOCh. sec, alcohol, tert, alcohol, phenylhydrozone, semicarbazone, more, less, acetals, ketals, silver mirror, test, urotropine, acetaldehyde cyanohydrin, lactic acid, benzoic acid, Sodalime, ethanoic acid, propanoic acid, electrolysis, Kolbe's electrolytic reaction, carbon dioxide, water, amides, alpha, halogen, phosphorus, weaker, stronger, ethyl alcohol, dibasic,monobasic, 2,2-dimethylpropanoic acid, `CH_(3)COCI`, acetic acid, `CH_(3)CH_(2)CH_(2)COOK`, enatiomers, diastereo, `K_(a)` `pk_(a)`, methanoic acid, higher, lower.)
Benzaldehyde undergoes ............ reaction on treatment with concentrated sodium hydroxide because it has ........

Explanation

To solve the question, we need to fill in the blanks with the appropriate words from the given options. The question states: "Benzaldehyde undergoes ............ reaction on treatment with concentrated sodium hydroxide because it has .........."

### Step-by-Step Solution:

1. **Identify the Reaction Type**:
- Benzaldehyde is an aromatic aldehyde. When treated with concentrated sodium hydroxide, it undergoes a specific type of reaction that is characteristic of aldehydes without alpha-hydrogens.
- The correct reaction is **Cannizzaro's reaction**. This reaction occurs in aldehydes that do not have alpha-hydrogen atoms.

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