A good quality of water will have:

The correct option is A high DO (Dissolved Oxygen)
Water contains oxygen dissolved in it, which is essential for all living beings, so, good quality of water must contain high amount of dissolved oxygen in it.

Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.

When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is being consumed by the bacteria. Since less dissolved oxygen is available in the water, fish and other aquatic organisms may not survive.

Hence, the only correct option is A.