Answer:
D) Nitrogen-fixing bacteria in root nodules of legumes.
Explanation:
Mutualism is when organisms of two different species interact benefiting both in some way. This can involve the exchange of resources, such as shelter, food or nutrients, or the exchange of services, such as protection, transportations, and healthcare. Mutualism is very important in ecology.
In this case, the nitrogen-fixing bacteria invade the root hairs of host plants, multiplying and stimulating the formation of root nodules, enlargements of plant cells and bacteria in intimate association. In the nodules, the bacteria transform free nitrogen to ammonia, wich the host plant uses for developing.
