The correct answer is option 4: Acoelomates. Acoelomates are animals that do not have a body cavity, also known as a coelom. Acoelomates lack the space between their digestive system and body wall that is filled with fluid in animals with a coelom. This absence of a body cavity results in a solid body structure without a separate fluid-filled cavity.
In contrast, option 1: Coelomates, refers to animals that possess a true body cavity called a coelom. Option 3: Pseudocoelomates, also have a body cavity, but it is not considered a true coelom as it is not completely lined by mesoderm. Option 2: Wild, is not a scientific term related to body cavities and is therefore incorrect.
Therefore, the animals in which the body cavity is absent are known as Acoelomates.