**The qualities aspired to obtain a good permanent magnet are high residual flux and high coercivity.**

**1. High residual flux:**
- Residual flux (Br) is a measure of the magnetic flux density that remains in a material after it has been magnetized to saturation and then the magnetic field is removed.
- A good permanent magnet should have a high residual flux, which means that it can retain a strong magnetic field even after the external magnetic field is removed.
- This property is important for applications where a strong and long-lasting magnetic field is required, such as in electric motors, generators, and magnetic separators.

**2. High coercivity:**
- Coercivity (Hc) is the measure of the ability of a material to resist demagnetization.
- A good permanent magnet should have a high coercivity, which means that it requires a large external magnetic field to demagnetize the material.
- High coercivity ensures that the magnet will retain its magnetization even in the presence of external magnetic fields or other demagnetizing influences.
- This property is crucial for applications where the magnet needs to maintain its magnetic field strength over a long period of time, such as in magnetic storage devices, magnetic sensors, and speakers.

**Explanation of the correct answer:**
- The correct answer is option D, which states that a good permanent magnet should have both high residual flux and high coercivity.
- Having high residual flux ensures that the magnet can generate a strong magnetic field, while high coercivity ensures that the magnet can retain this magnetic field over time, even in the presence of external influences.
- Therefore, a combination of these two qualities is essential for a permanent magnet to be considered good and suitable for various applications in electrical engineering.
- A magnet with only high residual flux and low coercivity would lose its magnetization easily, while a magnet with only high coercivity and low residual flux would not be able to generate a strong magnetic field.
- Therefore, option D, which includes both high residual flux and high coercivity, is the correct answer for obtaining a good permanent magnet.