The order in which the following oxides are arranged according to decreasing basic nature is

Options

A. `Na_(2)O,MgO,Al_(2)O_(3),CuO`
B. `CuO,Al_(2)O_(3),MgO,Na_(2)O`
C. `Al_(2)O_(3),CuP,MgO,Na_(2)O`
D. `CuO,MgO,Na_(2)O_(3)`

Explanation

To determine the order of the given oxides according to their decreasing basic nature, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Metals in the Oxides**:
The oxides mentioned are Na2O (sodium oxide), MgO (magnesium oxide), Al2O3 (aluminum oxide), and CuO (copper oxide). We need to focus on the metals: sodium (Na), magnesium (Mg), aluminum (Al), and copper (Cu).

2. **Understand Basic Nature of Oxides**:
Basic nature of metal oxides generally decreases as we move from left to right across a period in the periodic table. Alkali metals and alkaline earth metals tend to form basic oxides, while metals towards the right (like aluminum and copper) form amphoteric or acidic oxides.

3. **Arrange Metals in the Periodic Table**:
- Sodium (Na) is in Group 1 (alkali metals).
- Magnesium (Mg) is in Group 2 (alkaline earth metals).
- Aluminum (Al) is in Group 13.
- Copper (Cu) is in Group 11.

4. **Determine Basic Nature Order**:
- Sodium oxide (Na2O) is the most basic because sodium is an alkali metal.
- Magnesium oxide (MgO) is next, as it is an alkaline earth metal.
- Aluminum oxide (Al2O3) is less basic than MgO because aluminum has some amphoteric character.
- Copper oxide (CuO) is the least basic since copper is a transition metal and tends to form acidic oxides.

5. **Final Order**:
Based on the above analysis, the order of the oxides according to decreasing basic nature is:
- Na2O > MgO > Al2O3 > CuO.

### Conclusion:
Thus, the correct order of the oxides according to their decreasing basic nature is: **Na2O > MgO > Al2O3 > CuO**.