With direct water cooling it is possible to have ratings of about

The other options are incorrect because they are not realistic ratings for direct water cooling systems. A 200 MW direct water cooling system would be too small for most power plants, and a 600 MW direct water cooling system would be too large and expensive.

Here is a brief explanation of each option:

• Option A: 200 MW. This is a realistic rating for a direct water cooling system. However, it is not a common rating, and it is not used in many power plants.
• Option B: 300 MW. This is a common rating for a direct water cooling system. It is used in many large power plants.
• Option C: 400 MW. This is a realistic rating for a direct water cooling system. However, it is not a common rating, and it is not used in many power plants.
• Option D: 600 MW. This is too large a rating for a direct water cooling system. It is not used in any power plants.