Anodised aluminium is:

Options

A. Al obtained at anode.
B. Al prepared electrolytically
C. Alloy of Al containing 95% of Al
D. Al electrolytially coated with aluminium oxide.

Explanation

To answer the question "Anodised aluminium is:", we need to analyze the options provided and understand the process of anodizing.

### Step-by-Step Solution:

1. **Understanding Anodizing**:
- Anodizing is an electrochemical process that converts the surface of aluminum into a decorative and durable oxide layer. This layer is known as anodic oxide.

2. **Analyzing the Options**:
- **Option A**: Aluminium obtained at anode - This is incorrect because anodizing is not about obtaining aluminum at the anode; it is about treating aluminum.
- **Option B**: Aluminium prepared electrolytically - This option is partially correct, as anodizing does involve an electrolytic process, but it does not fully describe what anodized aluminum is.
- **Option C**: Alloy of aluminium containing 95% of aluminium - This is incorrect as anodizing does not refer to an alloy.
- **Option D**: Aluminium electrolytically coated with aluminium oxide - This is the correct answer. Anodized aluminum refers to aluminum that has been treated to form a protective layer of aluminum oxide through an electrolytic process.

3. **Conclusion**:
- The correct answer is **Option D**: Aluminium electrolytically coated with aluminium oxide.