The most ancient branching point in the phylogeny of animals is the one that distinguishes between having:
a. single cellularity and multicellularity.
b. radial or bilateral symmetry.
c. defined tissues or no tissues.
d. growth by molting or by continuous additions.
e. first gut opening develop into a mouth and first gut opening develop into an anus.
Ans: c. defined tissues or no tissues.
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