Nerve cells form long projections called
soma
axons
dendrites
synapses

The correct answer is the second option axon.

Explanation:

Neurons or nerve cells is a cell that transfers electrical signals. Nerve cells are the structural and functional units of the human nervous system. Every nerve cell is made up of 3 parts, a cell body called soma, dendrites and an axon.

The soma or cell body forms an elongated projection, called axon. Axon is responsible for sending electrochemical signals with the help of elaborate ion transport.  Some nerve cells have a myelin sheath covering around the axon to facilitate signals faster.  

Thus, the correct answer is the second option, Axon.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.