先通读下面的短文，然后根据短文内容和所给首字母，在空格内填入一个适当的词，使短文意思完整。
In many countries, people t__________ by car or by bike. They also get from place to place using p__________ transport such as buses and trains. However, some people live in parts of the world where it is i__________ to build roads.
It is difficult to w__________in snow but easy to ski over it. So in places like Alaska, people use skis. If they want to go faster, they get dogs to p__________ them on sleds(雪橇). Riding a snowmobile(雪地摩托) is a more m__________ , but expensive way of getting around on snow.
In desert(沙漠) like the Sahara in North Africa, people s__________get around on camels. Camels survive w__________ in the desert, not because they can s__________ water in their bodies though! They can survive without water for two weeks and without f__________for up to a month. H__________ can only go without water for about three to five days.