(Aldol, benzoin, +I, -I, decreases, increases, cyanohydrin, lactic acid, tartaric acid, yellow, white, acetone, penta-3-one, `PCl_(3)`, PCl, benzal chloride, methanol, propanoic acid, ethanol, KOH, KCN, `alpha`-hydrogen atoms, no `alpha`-hydrogens, Cannizzaro's, absence, presence)
Benzaldehyde undergoes ......... reaction on treatment with concentrated sodium hydroxide because it has .......... atom.

Explanation

To solve the question, we need to fill in the blanks regarding the reaction of benzaldehyde with concentrated sodium hydroxide.

### Step-by-Step Solution:

1. **Identify the Reaction Type**:
Benzaldehyde is an aldehyde that lacks alpha-hydrogen atoms. Therefore, it undergoes the Cannizzaro reaction when treated with a strong base like concentrated sodium hydroxide.

**Fill in the first blank**: "Benzaldehyde undergoes **Cannizzaro's** reaction..."
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