Ethanal, $\text{CH}_3\text{CHO}$, can be reduced with $\text{NaBH}_4$ in aqueous ethanol. This proceeds by nucleophilic addition. What might be the first step in this mechanism?
- Aattack of an $\text{H}^-$ ion at the carbon atom of the carbonyl group
- Battack of an $\text{H}^-$ ion at the oxygen atom of the carbonyl group
- Cattack of an $\text{H}^+$ ion at the carbon atom of the carbonyl group
- Dattack of an $\text{H}^+$ ion at the oxygen atom of the carbonyl group