Answer:
The major sources of global commercial energy are oil, gas and coal.
The three major sources of global commercial energy are, (fossil fuels) petroleum, natural gas, and coal. (Cunningham & Cunningham, 2009, p. 283)
Reference
Cunningham, W.P. and Cunningham, M.A. (2008). Principles of environmental science: Inquiry and applications (5th ed.). New York: McGraw-Hill