(a) Bilateral symmetry involves the division of the animal through a sagittal plane, resulting in two mirror-image, right and left halves. Animals with bilateral symmetry have a "head" and "tail" (anterior vs. posterior), front and back (dorsal vs. ventral), and right and left sides.
Examples: butterfly, crab, or humans.
(b) A coelom is a fluid-filled body cavity that is completely lined by tissue created from the mesoderm, the middle layer of the primary cells found in an embryo. It is typically found in multicellular organisms, which are living things that have more than one cell.
Example: Vertebrates.
(c) Triplobalstic condition is having three germ layers formed during the early embryo through the process of gastrulation. There are three types of germ layers, they are ectoderm, mesoderm, and endoderm. These layers give rise to different organs of the body during organogenesis.
All animals except Porifera, Cnidaria, and Ctenophora have these three germ layers.These animals are called triploblastic animals.