Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

[EX Q]: Passage: Peyton Manning became the first quarterback ever to lead two different teams to multiple Super Bowls. He is also the oldest quarterback ever to play in a Super Bowl at age 39. The past record was held by John Elway, who led the Broncos to victory in Super Bowl XXXIII at age 38 and is currently Denver's Executive Vice President of Football Operations and General Manager. Question: How old was Peyton Manning when he played in Super Bowl 50?
[EX A]: 39

[EX Q]: Passage: Contrary to popular belief, Genghis Khan did not conquer all the areas ultimately part of the Mongol Empire. At the time of his death, the Mongol Empire stretched from the Caspian Sea to the Sea of Japan. The empire's expansion continued for a generation or more after Genghis's death in 1227. Under Genghis's successor Ögedei Khan the speed of expansion reached its peak. Mongol armies pushed into Persia, finished off the Western Xia and the remnants of the Khwarezmids, and came into conflict with the imperial Song dynasty of China, starting a war that lasted until 1279 and that concluded with the Mongols gaining control of all of China. They also pushed further into Russia and eastern Europe. Question: What body of water sat to the west of the Mongol Empire when Genghis Khan died?
[EX A]: Caspian Sea

[EX Q]: Passage: The study also found that there were two previously unknown but related clades (genetic branches) of the Y. pestis genome associated with medieval mass graves. These clades (which are thought to be extinct) were found to be ancestral to modern isolates of the modern Y. pestis strains Y. p. orientalis and Y. p. medievalis, suggesting the plague may have entered Europe in two waves. Surveys of plague pit remains in France and England indicate the first variant entered Europe through the port of Marseille around November 1347 and spread through France over the next two years, eventually reaching England in the spring of 1349, where it spread through the country in three epidemics. Surveys of plague pit remains from the Dutch town of Bergen op Zoom showed the Y. pestis genotype responsible for the pandemic that spread through the Low Countries from 1350 differed from that found in Britain and France, implying Bergen op Zoom (and possibly other parts of the southern Netherlands) was not directly infected from England or France in 1349 and suggesting a second wave of plague, different from those in Britain and France, may have been carried to the Low Countries from Norway, the Hanseatic cities or another site. Question: What do the strains of y. pestis suggest abut the plague?
[EX A]:
the plague may have entered Europe in two waves