Bipolar nerve cells are present in

Four healthy people in their twenties were involved in injuries resulting in damage and death of a few cells of the following types. Which of these cells are least likely to be replaced by new cells?

Analogy type question:
$(1)$ Myelinated nerve fiber is covered by Schwann cells : The gap between two adjacent myelin sheaths : .......
$(2)$ Multipolar neuron : One axon and two or more dendrites :: Bipolar neuron : ..........

The energy required during the transmission of a nerve impulse is provided by:

Four healthy people in their twenties faced injuries resulting in damage and death of a few cells given below. Which of the cells are least likely to be replaced by new cells?

In polio,the legs become paralyzed and useless. What is the reason for this?