Pick up the reactions form the following where a water molecule is removed and reduction of `NAD^(+)` does not occur in the reactions of respiration
(i) Succinic acid to fumaric acid
(ii) Malic acid to oxalacetic acid
(iii) 2-phosphoglycerate to phosphoenol pyruvic acid
(iv) Pyruvic acid to acetyl CoA

Options

A. I, iv
B. I, ii
C. ii, iii
D. I, iii.

Answer

To solve the problem, we need to analyze each of the given reactions and determine whether a water molecule is removed and whether the reduction of NAD⁺ occurs.

### Step-by-Step Solution:

1. **Analyze Reaction (i): Succinic acid to fumaric acid**
- In this reaction, succinic acid is oxidized to fumaric acid.
- During this process, a water molecule is indeed removed.
- However, NAD⁺ is not reduced; instead, FAD is reduced to FADH₂.
- **Conclusion:** This reaction fits the criteria (water removed, no NAD⁺ reduction).

2. **Analyze Reaction (ii): Malic acid to oxaloacetic acid**
- In this reaction, malic acid is oxidized to oxaloacetic acid.
- This reaction involves the reduction of NAD⁺ to NADH.
- **Conclusion:** This reaction does not fit the criteria (NAD⁺ is reduced).

3. **Analyze Reaction (iii): 2-phosphoglycerate to phosphoenol pyruvic acid**
- In this reaction, 2-phosphoglycerate is converted to phosphoenol pyruvic acid.
- Water is removed during this conversion.
- There is no reduction of NAD⁺ in this reaction.
- **Conclusion:** This reaction fits the criteria (water removed, no NAD⁺ reduction).

4. **Analyze Reaction (iv): Pyruvic acid to acetyl CoA**
- In this reaction, pyruvic acid is converted to acetyl CoA.
- During this process, NAD⁺ is reduced to NADH.
- **Conclusion:** This reaction does not fit the criteria (NAD⁺ is reduced).

### Final Answer:
The reactions where a water molecule is removed and reduction of NAD⁺ does not occur are:
- (i) Succinic acid to fumaric acid
- (iii) 2-phosphoglycerate to phosphoenol pyruvic acid