Which of the following organisms is an acoelomate? . earthworm . insect . flatworm . clam .

The correct answer is option C, Flatworm

Reason -

Acoelomate are group of organisms that do not have body cavity or coelem. They do not have a fluid filled cavity and have a triploblastic body plan.  

Since Flatfworms lacks the body cavity and so they are considered as Acoelomate. They are invertebrate organisms having unsegmented body and also possesses bilateral symmetry. They are parasite who live inside other animals and feed on their digested food. They possess a simple digestive tract, nervous system, and excretory system.

materials water oxygen those are the things i can think of in this moment.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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