Among the oxides, `Mn_2O_7 (I), V_2O_3 (II), V_2O_5 (III), CrO (IV)` and `Cr_2O_3 `(V) the basic oxides are

Options

A. I and II
B. II and III
C. III and IV
D. II and IV

Explanation

To determine which of the given oxides are basic, we need to analyze the oxidation states of the metals in each oxide and their corresponding acidic or basic nature.

### Step-by-Step Solution:

1. **Identify the Oxides**: The given oxides are:
- \( \text{Mn}_2\text{O}_7 \) (I)
- \( \text{V}_2\text{O}_3 \) (II)
- \( \text{V}_2\text{O}_5 \) (III)
- \( \text{CrO} \) (IV)
- \( \text{Cr}_2\text{O}_3 \) (V)

2. **Determine the Oxidation States**:
- For \( \text{Mn}_2\text{O}_7 \):
\[ 2x + 7(-2) = 0 \implies 2x - 14 = 0 \implies x = +7 \]
- For \( \text{V}_2\text{O}_3 \):
\[ 2y + 3(-2) = 0 \implies 2y - 6 = 0 \implies y = +3 \]
- For \( \text{V}_2\text{O}_5 \):
\[ 2z + 5(-2) = 0 \implies 2z - 10 = 0 \implies z = +5 \]
- For \( \text{CrO} \):
\[ p + 1(-2) = 0 \implies p - 2 = 0 \implies p = +2 \]
- For \( \text{Cr}_2\text{O}_3 \):
\[ 2q + 3(-2) = 0 \implies 2q - 6 = 0 \implies q = +3 \]

3. **Classify the Oxides**:
- **Acidic Oxides**: Generally, oxides with high oxidation states are acidic.
- \( \text{Mn}_2\text{O}_7 \) (Mn is +7) - Acidic
- \( \text{V}_2\text{O}_5 \) (V is +5) - Acidic
- **Basic Oxides**: Oxides with low oxidation states are basic.
- \( \text{CrO} \) (Cr is +2) - Basic
- \( \text{V}_2\text{O}_3 \) (V is +3) - Basic
- **Amphoteric Oxides**: Oxides that can act as both acids and bases, typically with intermediate oxidation states.
- \( \text{Cr}_2\text{O}_3 \) (Cr is +3) - Amphoteric

4. **Conclusion**: The basic oxides among the given options are:
- \( \text{CrO} \) (IV)
- \( \text{V}_2\text{O}_3 \) (II)

Thus, the basic oxides are \( \text{CrO} \) and \( \text{V}_2\text{O}_3 \).

### Final Answer:
The basic oxides are \( \text{CrO} \) and \( \text{V}_2\text{O}_3 \) (Options II and IV).

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