`(B)overset(Θ)(OH)larr CH_(2)=CH-CHO overset(AI(OEt)_(3))rarr (A)`

Explanation

To solve the problem step by step, we will analyze the reaction of acrolein with the given reagents and determine the products A and B.

### Step 1: Identify the Reactant
The reactant given is acrolein, which has the structure:
\[ \text{CH}_2=CH-CHO \]

### Step 2: Reaction with Aluminium Ethoxide
The first reagent is aluminium ethoxide, which suggests a reaction similar to the Cannizzaro reaction. In this reaction, aldehydes without alpha-hydrogens undergo disproportionation.
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