Cephalizationa) is a feature of most invertebrates, including the spongesb) is characterized by the concentration of sensory organs in the anterior endc) occurs in marine protozoad) results when the brain does not develop properly

b) is characterized by the concentration of sensory organs in the anterior end.

Explanation:

Cephalization is a feature of most animals (but not all) in which sensory organs (photoreceptor, chemoreceptors, mechanoreceptors, etc) and nerves (can be a brain) are localized together in the anterior end of them.  This "end" is what we called "head".

Sponges don't have "head" and this feature is not exclusive of invertebrates, so option (a) is wrong.  Similarly, option (c) is incorrect too because cephalization is an animal characteristic not of protozoa.  

Option (d) can't be true because cephalization refers to a localized cluster of specialized sensory and nervous tissues and organs in the "head-end"; it is not necessary that there be a complex brain. However, when a brain is present, there is cephalization too.

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