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Every winter in Alaska a race is held. But this is no ordinary race. Teams of dogs pull sleds（雪橇）along the snow and ice, 61 (carry) up to 500 kg of supplies. A single driver is in charge of each team, and stands on the sled. This race 62 (know) as Iditarod runs from the town of Anchorage to the village of Nome, a journey of more than l,800 kilometers. It usually takes the teams about ten days to complete the course.
The Iditarod is usually run in 63 (extreme) difficult weather conditions. Daytime 64 (temperature) range from zero to minus 40 degrees. Visibility（能见度）is often very poor, 65 drivers never allow 66 (them) to become separated from their team of dogs. Indeed, the drivers depend almost entirely 67 the dogs for their survival.
The origin of the race 68 (go) back many years to a time 69 some medicine needed to be taken from Anchorage to Nome, a very remote village. Because of severe weather, the only way to
send the medicine was to use dogs. Happily, the medicine was delivered just in time to save lives. To celebrate the heroic journey, Alaskans 70 (develop) the Iditarod.