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.