Which feature is not a characteristic of Protochordata?
(a)Bilateral Symmetry.
(b)Coelom.
(c)Notochord.
(d)Jointed legs.

Hint: Protochordate is an informal category of organisms to explain the invertebrates that are closely associated with vertebrates.This group composed of the Phylum Hemichordata and also the Subphylum Urochordata and Cephalochordata.

Complete answer:
Jointed appendages are the characteristic feature of Arthropoda which has most of the insects. This group consists of the Phylum Hemichordata and the Urochordata and Cephalochordata.
The Phylum Hemichordata has marine worms that share some, but not all of the characteristics of chordates. These animals have pharyngeal gill slits and a dorsal nerve cord, which is typically solid. The three body parts of them are proboscis, collar, and trunk. What was once thought to be a notochord is no longer considered homologous. Acorn worms are samples of hemichordates.
The Urochordates and Cephalochordates are protochordate but belong to the Chordata.
Jointed legs are the characteristic of Arthropods, Notochord is the character of Chordata, bilateral symmetry is the division of an organism into 2 equal halves when passed through the centre.

So, the correct answer is, “Jointed legs.”

Note: - These animals have some pharyngeal gill slits and a dorsal nerve cord, which is usually solid. What was once thought to be a notochord is not any longer considered homologous. Acorn worms are examples of hemichordates.
-The main difference between chordates and protochordate is that the chordates are the animals that have distinct characteristics such as a notochord, dorsal nerve cord, pharyngeal slits, and a muscular tail whereas the protochordate is an informal group of invertebrates within chordates.