a) are found only in the central nervous system
b) carry electrical signals along the length of an axon
c) are gaps between neurons where chemical signals are used to transmit information
d) allow electrical signal to jump between myelin segments

(c). are gaps between neurons where chemical signals are used to transmit information

Explanation:

Synapses can be defined as junction present between two nerve cells, through which nerve impulses are transmitted by using chemical signals or neurotransmitters. The synapses represent a small gaps that separate two neurons.

The neurotransmitters are released by ending of presynaptic neuron and allows transmission of signals from presynaptic neuron to postsynaptic neuron. Hence, synapses are necessary for unidirectional flow of impulses.

Thus, the correct answer is option (c).