The organism that has a hydrostatic skeleton is

The organism that has a hydrostatic skeleton is an earthworm. A hydrostatic skeleton is a structure found in soft-bodied invertebrates, which uses the pressure of fluid-filled body cavities to provide support and movement. In earthworms, the hydrostatic skeleton is made up of a fluid-filled body cavity called the coelom, which is surrounded by muscle tissue. When the circular muscles in one segment contract, the fluid is pushed towards the longitudinal muscles in the next segment, causing them to extend and push the worm forward. The hydrostatic skeleton also allows the earthworm to change its shape and move through narrow spaces. In contrast, Tilapia, Hydra, and mosquito larva do not have a hydrostatic skeleton. Tilapia is a fish that has a bony skeleton, while Hydra is a freshwater animal that has a simple body structure without a well-defined skeleton. Mosquito larvae also have a soft body and use their muscles to move, but they do not have a hydrostatic skeleton. Therefore, the correct answer is "earthworm", as it is the organism that has a hydrostatic skeleton, which is a structure found in soft-bodied invertebrates, that uses the pressure of fluid-filled body cavities to provide support and movement.