Final answer:
The false statement about the phylum Chordata is that all chordates replace the notochord with a spinal column during development. Not all chordates undergo this transformation as some retain the notochord throughout their lives.
Step-by-step explanation:
The statement that is FALSE about the phylum Chordata is option c. 'In all chordates, the notochord is replaced by the spinal column during development.' This statement is incorrect because, while it is true for vertebrates (which are a sub-group within the phylum Chordata), not all chordates replace the notochord with a spinal column. In some chordates, the notochord persists throughout life.
The correct characteristics of chordates are that they all possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-a nal tail at some stage of their development. Furthermore, the pharyngeal slits in vertebrate fishes develop into gills, and in humans and other vertebrates, they have different functions or may not be present in the adult form.