The correct answer is option 4: Green plants. While all living organisms can produce some amount of greenhouse gases, green plants are more likely to produce greenhouse gases such as nitrous oxide and methane. This is because green plants perform a process called respiration, which involves breaking down organic matter and releasing carbon dioxide. However, in environments with low oxygen levels, such as wetlands and rice paddies, green plants also produce methane as a byproduct of their metabolism. Methane is a potent greenhouse gas, contributing to global warming. Nitrous oxide is also produced in small amounts by green plants as a result of certain microbial processes in the soil. It is important to note that while green plants do produce greenhouse gases, they also play a crucial role in mitigating climate change by absorbing carbon dioxide through photosynthesis.