The correct answer is option 'D' - Philippines.

The Dapog method of rice nursery is a technique that was developed in the Philippines. It is a traditional method of raising rice seedlings in a nursery before transplanting them to the main field. This method has been widely used by Filipino farmers for many years and has proven to be effective in increasing rice productivity.

Here is an explanation of the Dapog method of rice nursery in detail:

1. Definition and Purpose:
- The Dapog method involves the use of small seedbeds or nurseries to grow rice seedlings before they are transplanted to the main field.
- The purpose of this method is to ensure the healthy growth of seedlings, improve their survival rate, and achieve higher yields in the main field.

2. Preparation of the Nursery:
- A suitable area of land is selected for the nursery, usually near a water source for irrigation.
- The land is plowed and leveled to create a smooth seedbed.
- The size of the nursery can vary depending on the number of seedlings needed.
- The nursery is divided into small plots or dapogs, usually measuring around 1.5 meters by 1.5 meters.

3. Seed Preparation and Sowing:
- High-quality rice seeds are selected and soaked in water for about 24 hours.
- The soaked seeds are then spread evenly on a clean cloth or mat to allow them to dry for a few hours.
- The dried seeds are sown in the prepared dapogs, with a recommended spacing of 2-3 seeds per hole.
- The depth of sowing is around 1-2 centimeters.

4. Water Management:
- After sowing, the nursery is irrigated with water to keep the soil moist.
- Excessive water should be avoided to prevent seed rot or fungal diseases.
- The water level is maintained at around 2-3 centimeters throughout the nursery.

5. Care and Maintenance:
- Weeding is an important aspect of the Dapog method. Weeds compete with rice seedlings for nutrients and sunlight, so regular weeding is necessary.
- Pests and diseases should be monitored and appropriate measures taken to control them.
- Fertilizers can be applied to the nursery if necessary, following recommended guidelines.

6. Transplanting:
- After about 25-30 days, when the seedlings have grown to a suitable size (around 10-15 centimeters), they are ready for transplanting.
- The seedlings are carefully uprooted from the nursery and transplanted to the main field.

Overall, the Dapog method of rice nursery is an effective technique for raising healthy rice seedlings before transplanting them to the main field. It helps to ensure better crop establishment and higher yields, contributing to improved rice production in the Philippines.