The structure labelled II is the clitellum. It is a prominent, swollen band on the body of an earthworm that secretes mucus for reproduction and forms the cocoon where eggs are deposited.

Here are the answers to questions 6 and 7.

6. The structure labelled II is the clitellum. It is a prominent, swollen band on the body of an earthworm that secretes mucus for reproduction and forms the cocoon where eggs are deposited.

   The final answer is $\boxed{\text{B}}$

7. The organism (an earthworm) is found in soils rich in humus. Humus is decomposed organic matter that provides nutrients and a suitable habitat for earthworms.

   The final answer is $\boxed{\text{A}}$