The correct working time in the paddy field in Kalpattu is option B, which is from 8.30 am to 4.30 pm. This answer can be determined by considering various factors such as the climate, labor laws, and the usual working hours in the agricultural sector.

**Climate and agricultural practices:**
Kalpattu is located in the state of Tamil Nadu in India. The region experiences a tropical climate, with hot and humid weather throughout the year. Paddy fields are typically flooded with water for the cultivation of rice, which requires a specific temperature and humidity range. Therefore, it is essential to consider the climatic conditions when determining the working hours in the paddy fields.

**Labor laws and regulations:**
Labor laws and regulations play a significant role in defining the working hours in any industry, including agriculture. In India, the labor laws vary from state to state. Tamil Nadu, where Kalpattu is located, follows the regulations set by the Factories Act, 1948, and the Shops and Establishments Act, 1947.

According to the Factories Act, the maximum working hours for adult workers in factories, including agricultural operations, is 9 hours per day or 48 hours per week. Additionally, the law requires a minimum of 30 minutes of rest after every 5 hours of work.

**Usual working hours in the agricultural sector:**
Considering the climate and labor laws, the usual working hours in the paddy fields in Kalpattu are likely to be determined to ensure the well-being and safety of the workers. Option B, which states the working hours from 8.30 am to 4.30 pm, aligns with the maximum working hours allowed per day as per the labor laws. This duration of 8 hours includes a one-hour lunch break and two 15-minute rest breaks, which are consistent with the legal requirements.

**Conclusion:**
Taking into account the climate, labor laws, and the usual working hours in the agricultural sector, option B, which indicates the working time from 8.30 am to 4.30 pm, is the correct answer. This timing ensures compliance with the labor laws while considering the specific requirements of paddy field cultivation in Kalpattu.

B