Answer:
An energy mutual fund
Step-by-step explanation:
An energy mutual fund is like a normal fund, with the difference that it invests your portfolio only on energy-sector companies, for example: oil companies, natural gas companies or coal companies (although these tend to be neither as profitable nor as common).
If you go to an energy mutual fund, you will be offered investment options such as common stock, preferred stock and corporate bonds, and you money will be spread in among those investment instruments. Your portfolio will be diversified in a sector that usually has good economic prospects.