Final answer:
The correct answer is C) all of the answers are correct, as a fluid-filled body cavity cushions and protects organs, acts as a hydrostatic skeleton, and allows independent organ movement.
Step-by-step explanation:
The advantages of a fluid-filled body cavity, like the coelom, provide several critical functions for the organisms that possess them. One notable function is that the internal organs are cushioned and protected from injury; this is crucial for maintaining the integrity and function of the organs in response to physical stress or impact. Another crucial role is acting as a hydrostatic skeleton, which is an internal system of support in certain soft-bodied animals. The fluid pressure within the cavity supports the body and facilitates movement, providing a structure against which muscles can contract. Additionally, the presence of a fluid-filled body cavity allows organs to grow and move independently of the outer body wall, which is beneficial for the development and function of these organs.
If we examine the options provided in the question, a fluid-filled body cavity such as the coelom indeed performs multiple functions, including cushioning and protecting internal organs (A), acting as a hydrostatic skeleton (B), and allowing organs to move independently of the body wall (D). Therefore, in the context of the question, the correct choice that encompasses all these functions would be (C) all of the answers are correct.