In the early days of arctic exploration, dogsled was often the only way to travel. The ice, snow, and extremely cold weather made using other animals, such as horses, impossible. Snowmobiles were not invented yet. Most explorers journeyed by ship until the ice made it impossible to continue. Then, they would switch to dogsled. The dogs, working together, were a well-oiled machine that could cover long distances in the cold. Sled dogs needed to have long, warm coats to survive the arctic temperatures. They had to be fast and able to run for long distances while pulling a heavy load. Most importantly, they had to work together as a team. This made northern dogs, such as Siberian huskies and Alaskan malamutes, the best choices for the sled teams. These dogs have long coats, with a double layer of fur to keep out the cold, and they have wide paws with webbed toes that act like snowshoes. They have been bred for more than 9,000 years to be working dogs in extreme winter weather. They are friendly, team-oriented, and purposeful dogs. In the days of the arctic explorers, the physical features and determined personalities of the sled dogs made long journeys in harsh conditions possible.

To be in the best condition for pulling heavy loads, the dogs needed a diet that was high in fat. They ate whale and seal blubber and fatty meats during their long journeys, which kept them strong and gave them energy to keep going. The dogs' paws also needed special care to make sure that they did not become injured by sharp ice or extreme cold. Treating the paws with fat or wax helped the dogs to run safely and comfortably.

Although the days of arctic explorers are long past, sled dogs continue to run through the snow and ice of the North. Dogsledding is now recognized as a sport, with many competitions taking place all over the world. One of the most well-known of these is the Iditarod, a race of almost 1,000 miles. It commemorates the Great Race of Mercy that took place in 1925 when dog sled teams were the only hope of a town that needed life-saving medicine. The race takes 8–11 days to complete and is run regardless of weather conditions. Teams of twelve or more dogs train with their handlers for years before competing. The race is long and one of the most challenging in the world. Dogs and their handlers must be in top physical condition to have any chance of winning.

During the race, the dogs get multiple rest stops and are checked by veterinarians to make sure they avoid injuries. They eat high-fat, high-protein foods to give them the energy to continue, just like the dogs of the arctic explorers did. With the same determination that drove the dogs of the 1925 Great Race of Mercy, the dogs competing in the Iditarod run through even the worst blizzards and race to win.

Which reason supports the author's point that dogsled was often the only way to travel in the early days of arctic exploration?

Sled dogs could travel in conditions that ships and other animals could not endure.
Many people used snowmobiles to travel over the snow, but the machines could get stuck.
Most explorers traveled the arctic by ship and used smaller boats to get around ice.
Dog sleds were heavy and required a special type of driver called a musher to navigate them.

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