Which of the following will be oxidised by `HIO_(4)`?
(A) `R-underset(O)underset(||)C-underset(O)underset(||)C-R`
(B) `R-underset(O)underset(||)C-underset(OH)underset("| ")"CH"-R`
(C) `{:(R-CH-CH_(2)-CH-R),(" | |"),(" OH OH"):}`
(D) `{:(R-CH-CH-R),(" | |"),(" OH OH"):}`

Options

A. 1, 2 and 3
B. 1, 3 and 4
C. 1, 2 and 4
D. 2, 3 and 4.

Explanation

To determine which of the given compounds will be oxidized by HIO4, we need to analyze each option based on the criteria for oxidation by HIO4. HIO4 oxidizes compounds that have:

1. More than 2 OH groups attached to adjacent carbon atoms.
2. One OH group and one carbonyl group (C=O) attached to adjacent carbon atoms.
3. Two carbonyl groups attached to adjacent carbon atoms.

Now, let’s analyze each option step by step.

### Step 1: Analyze Option (A)
**Compound:** `R-underset(O)underset(||)C-underset(O)underset(||)C-R`

- This compound has two carbonyl groups (C=O) attached to adjacent carbon atoms.
- **Conclusion:** This compound can be oxidized by HIO4.

### Step 2: Analyze Option (B)
**Compound:** `R-underset(O)underset(||)C-underset(OH)underset("| ")"CH"-R`

- This compound has one carbonyl group (C=O) and one hydroxyl group (OH) attached to adjacent carbon atoms.
- **Conclusion:** This compound can also be oxidized by HIO4.

### Step 3: Analyze Option (C)
**Compound:** `{:(R-CH-CH_(2)-CH-R),(" | |"),(" OH OH"):}`

- This compound has two hydroxyl groups (OH) attached to adjacent carbon atoms.
- **Conclusion:** This compound can be oxidized by HIO4.

### Step 4: Analyze Option (D)
**Compound:** `{:(R-CH-CH-R),(" | |"),(" OH OH"):}`

- This compound has two hydroxyl groups (OH) attached to adjacent carbon atoms.
- **Conclusion:** This compound can also be oxidized by HIO4.

### Final Conclusion
Based on the analysis:
- **Options that can be oxidized by HIO4:** (A), (B), (C), and (D).
- Therefore, the correct answer is that all options (A), (B), (C), and (D) can be oxidized by HIO4.