A group of acidic oxide is

Options

A. `CrO_(3),Mn_(2)O_(7)`
B. `ZnO,Al_(2)O_(3)`
C. `CaO,ZnO`
D. `Na_(2)O, Al_(2)O_(3)`

Explanation

To determine a group of acidic oxides, we need to identify the oxides that exhibit acidic properties. Acidic oxides are generally formed from non-metals or certain metals in higher oxidation states. Let's analyze the given options step by step.

### Step 1: Identify the oxides
The question mentions the following oxides:
1. \( \text{CrO}_3 \) (Chromium trioxide)
2. \( \text{Mn}_2\text{O}_7 \) (Manganese heptoxide)
3. \( \text{ZnO} \) (Zinc oxide)
4. \( \text{Al}_2\text{O}_3 \) (Aluminum oxide)

### Step 2: Classify the oxides
Now, we will classify these oxides based on their acidic or basic nature:
- **Acidic Oxides:**
- \( \text{CrO}_3 \) is an acidic oxide because it reacts with water to form an acid (\( \text{H}_2\text{CrO}_4 \)).
- \( \text{Mn}_2\text{O}_7 \) is also an acidic oxide, as it forms \( \text{H}_2\text{MnO}_4 \) when reacted with water.

- **Amphoteric Oxides:**
- \( \text{ZnO} \) can act as both an acidic and basic oxide, depending on the reaction conditions.
- \( \text{Al}_2\text{O}_3 \) is also amphoteric, showing both acidic and basic properties.

### Step 3: Identify the group of acidic oxides
From the analysis, we see that the oxides \( \text{CrO}_3 \) and \( \text{Mn}_2\text{O}_7 \) are clearly acidic. Therefore, the group of acidic oxides identified here is:

**Group of Acidic Oxides: \( \text{CrO}_3 \) and \( \text{Mn}_2\text{O}_7 \)**

### Conclusion
The correct answer to the question "A group of acidic oxide is" is \( \text{CrO}_3 \) and \( \text{Mn}_2\text{O}_7 \).

---