The correct answer is      (A.) Propane

Yep, propane. When was the last time you thought about propane, anyway? Perhaps when you opened the valve of your backyard barbecue? Well, propane plays have been on fire. Their share prices have doubled and even tripled off last year's lows, but the good news is yields of up to 10% can still be found.

Although some 25,000 firms distribute the environmentally friendly fuel in the U.S., dozens of diversified energy companies also market the fuel. But the number of more or less pure propane plays that trade on U.S. exchanges can be counted on the fingers of one hand, and they're hot. Two are up around +100% off their late 2008 lows. Two are up about +140%. These results are all the more stunning when compared to the S&P 500's +60% climb off its bottom. Despite these huge rallies, yields average a juicy 8.8%, 3.5 times more than the 2.4% average of stocks in the S&P 500.

What's behind the distribution growth? For starters, the companies are Master Limited Partnerships (MLPs), which is another way of saying these companies are designed to be cash cows. They don't pay income taxes but instead pass along at least 90% of their taxable earnings to investors (who are then taxed on the earnings).

Besides their corporate structures, propane companies are sizzling because the 50 million Americans who consume propane in some form are usually loyal to their providers in the long term. (Switching often involves digging up the backyard to achieve negligible savings.) Moreover, billing practices can make the benefits of switching hard to quantify (think of your electric bill). Acquisitions also can boost sales but also improve profit margins, which has helped the propane majors grow sales an average +19.7% annually during the past five years in a relatively stable market.

There's no question propane stocks offer high yields supported by steady cash flow and growing earnings, but what do you do with this information? Well, StreetAuthority editor Carla Pasternak has figured it out. In her latest issue of the High-Yield Investing newsletter, Carla offers an in-depth analysis of the propane industry and shares picks that could certainly heat up your portfolio. To learn the names of these securities, and to learn more about High-Yield Investing, please visit this link.