Planet Earth’s Windiest Observatory
Step outside into blowing snow, freezing fog, 45 mph winds with hurricane-force gusts, and a –50° Fahrenheit windchill. Welcome to a typical January day at the Mount Washington Observatory. [A] Weather conditions at this facility, which sits atop its (46) namesake’s 6,288-foot peak in New Hampshire, has earned (47) the location the nickname “Home of the World’s Worst Weather.”
 [B] Though somewhat diminutive compared to other mountains, (Colorado’s Pikes Peak (48), for example, is more than twice its height), Mount Washington is the tallest peak in the Presidential Range (49).The peak stands at the confluence of three major storm tracks, and its steep slopes force (50) rising winds to accelerate. In fact, scientists in 1934 recorded a surface wind speed (of 231 mph) (51): one of the fastest ever recorded.
 In one study, researchers used a laser beam and advanced optical techniques to measure winds. The observatory also keeps detailed weather records that scientists have used to track climate trends and weather patterns. The (52) observatory has also advanced scientists’ understanding of clouds, of ice physics (53), and the atmosphere.
 To conduct all this research, staff are on-site year-round. Observers, who work (54) several twelve-hour shifts over the course of a week. To change personnel in winter, though (55) , crews ascend the mountain in a vehicle, gripping (56) the snow using revolving tracks similar to those on a military tank. Observers go outside every hour to gather data, which they send to the National Weather Service. [C]
 Though isolated, the Mount Washington Observatory offers weather enthusiasts many ways to get involved. The observatory takes volunteers and accepts interns, who assist with research. The( 57 ) bold can take part in educational trips to the summit in winter. [D] For those who are planning to make a trip to Mount Washington (58), the observatory has a website with live video feeds of the summit.
A. NO CHANGE
B.speed of 231 mph—
C.speed of 231 mph;
D.speed, of 231 mph