In Oppenauer's oxidation,

Options

A. secondary alcohol is oxidised to carboxylic acid in acetone solvent using aluminium tertiary butoxide
B. secondary alcohol is oxidised to carboxylic acid without affecting the `C=C` or `C-=C` bond by aluminium tertiary butoxide in acetone solvent
C. secondary alcohol is oxidised to ketone without affecting
the `C=C` or `C-=C` bond by aluminium tertiary butoxide
D. secondary alcohol is oxidised to ketone by chromic acid - pyridine complex.

Explanation

### Step-by-Step Solution:

1. **Understanding Oppenauer's Oxidation**: Oppenauer's oxidation is a method used to oxidize secondary alcohols to ketones using aluminum tert-butoxide as a reagent in the presence of acetone.

2. **Identifying the Reactants**: The reaction involves a secondary alcohol (R1CHOH-R2) and aluminum tert-butoxide (Al(OC(CH3)3)3) in the presence of acetone (CH3COCH3).

3. **Reaction Mechanism**: In the presence of aluminum tert-butoxide, the secondary alcohol undergoes oxidation to form a ketone (R1C(=O)R2). The aluminum tert-butoxide acts as a Lewis acid, facilitating the removal of a hydrogen atom from the alcohol.

4. **Formation of Products**: The products of the reaction are:
- A ketone (R1C(=O)R2)
- An alcohol (CH3CHOHCH3) which is not oxidized in this process.

5. **Evaluating the Statements**: The question provides four statements regarding Oppenauer's oxidation. We need to determine which statements are correct:
- The secondary alcohol is oxidized to a ketone.
- Other oxidizable groups remain unaffected.
- The reaction does not involve chromic acid or pyridine, which are not part of this oxidation method.

6. **Conclusion**: Based on the understanding of Oppenauer's oxidation, the correct statement is that secondary alcohols are oxidized to ketones without affecting other oxidizable groups. Therefore, the correct answer is option number 3.