Option 1: The statement in option 1 suggests that organic farming does not reduce CO2 emissions. This is false. Organic farming practices such as the use of cover crops and composting can help sequester carbon in the soil, thereby reducing CO2 emissions.

Option 2: The statement in option 2 suggests that organic farming leads to toxic effects. This is false. Organic farming avoids the use of synthetic pesticides, fertilizers, and genetically modified organisms, reducing the risk of exposure to harmful chemicals.

Option 3: The statement in option 3 suggests that organic farming improves the water-retention capacity of the soil. This is true. Organic farming practices, such as the use of organic matter and cover crops, can improve soil structure and increase water infiltration and retention.

Overall, the correct answer is option 4. Organic farming can reduce CO2 emissions, does not lead to toxic effects, and can improve the water-retention capacity of the soil.