If microbial fuel cells convert chemical energy into a flow of electrons, then what do microbial fuel cells convert chemical energy into?

Answer choices:
- rays or beams
 - transportation technology
 - Deoxyribonucleicacid
 - flow of electrons
 - hydrogen and oxygen
 - deoxyribonucleic acid
 - an engine
 - heating liquids

 

    flow of electrons      