The correct answer is option (A) no specialized neurons.
Nerve net refers to the simplest and the primitive form of the nervous system found in multicellular oraganisms. It is found in the members of Cnidaria, Ctenophora and Echinodermata. Nerve net provides the ability to sense objects, food particles by the presence of the sensory neurons in it. A nerve net is made up of diffuse network of cells forming a ganglion but does not form a brain. Since it does not form a brain it lacks the specialized neurons. It is made up of the sensory neurons that sense the stimulus and the motor neurons that produce a reaction to the stimulus.