Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Ex Input:
In the 1950s, a family that owned a farm near Beulah, Michigan kept a bull chained to an elm . The bull paced around the tree, dragging the heavy iron chain, which led to a groove in the bark . The groove deepened over the years. Though for whatever reason, it did not kill the tree. After some years, the family took their bull away. They cut the chain, leaving the loop around the tree and one link hanging down. Then one year, agricultural disaster struck Michigan in the form of Dutch Elm Disease. All of the elms lining the road leading to the farm became infected and died. Everyone thought that the old elm would be the next. The farm owners considered doing the safe thing: pulling it out and cutting it up into firewood before it died. But they simply could not bring themselves to do it. It was as if the old tree had become a family friend. So they decided to let nature take its course. Amazingly, the tree did not die. Nobody could understand why it was the only elm still standing in the county! Plant experts from Michigan State University came out to observe the tree. They observed the scar left by the iron chain, now almost completely covered by bark. The experts decided that it was the chain that saved the elm's life. They reasoned that the tree must have absorbed so much iron from the chain that it became immune to the virus. It's said that what doesn't kill you will make you stronger. Or, as Earnest Hemingway put it, "Life breaks us all, but afterwards, many of us are strongest at the broken places."

Ex Output:
What actually saved the elm?


Ex Input:
Bimberamala River, a perennial river of the Clyde River catchment, is located in the Southern Tablelands and the upper ranges of the South Coast regions of New South Wales, Australia.

Ex Output:
What body of water does Bimberamala River join?


Ex Input:
Once in a blue moon, there is one on New Year's Eve. Revelers ringing in 2010 will be treated to a so-called blue moon. According to popular definition, a blue moon is the second full moon in a month. But don't expect it to be blue - the name has nothing to do with the color of our closest celestial neighbor. A full moon occurred on December 2. It will appear again on Thursday in time for the New Year's countdown. The New Year's Eve blue moon will be visible in the United States, Canada, Europe, South America and Africa. For partygoers in Australia and Asia, the full moon does not show up until New Year's Day, making January a blue moon month for them. A full moon occurs every 29.5 days, and most years have 12. On average, an extra full moon in a month - a blue moon - occurs every 2.5 years. The last time there was a lunar double take was in May 2007. New Year's Eve blue moons are rarer, occurring every 19 years. The last time was in 1990; the next one won't come again until 2028. "Blue moons have no astronomical significance," said Greg Laughlin, an astronomer at the University of California. "'Blue moon' is just a name in the same sense as a 'hunter's moon'(a full moon in octorber) or a 'harvest moon,'" Laughlin said in an e-mail. The popular definition of blue moon came about after a writer for Sky & Telescope magazine in 1946 misinterpreted the Maine Farmer's Almanac and labeled a blue moon as the second full moon in a month. In fact, the almanac defined a blue moon as the third full moon in a season with four full moons.

Ex Output:

Which full moon should be called blue moon according to the original definition?