The correct answer is option 2: Platyhelminthes.

To understand why Platyhelminthes is the correct answer, let`s break down the criteria given in the question. The question states that the animal has a bilaterally symmetrical body, which means its left and right sides are mirror images of each other. This characteristic is found in many organisms, but we need to consider the other criteria as well.

The question also mentions that the animal has a triploblastic body, which means it has three germ layers: the ectoderm, mesoderm, and endoderm. These layers give rise to various tissues and organs in the body.

Finally, the question states that the animal does not have a true internal cavity or coelom. A true coelom is a fluid-filled cavity between the body wall and the gut. It is found in organisms belonging to certain phyla such as Annelida (option 4).

Considering all these criteria, we can conclude that Platyhelminthes (option 2) is the correct answer. Platyhelminthes, commonly known as flatworms, have a bilaterally symmetrical, triploblastic body without a true coelom. They are found