In many countries, people t (1) by car or by bike. They also get from place to place using p__________(2) transport such as buses and trains. However, some people live in parts of the world where it is I (3) to build roads. In these places, animals or other f (4) of transport have to be used. It is difficult to w (5) 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 (6) them on sleds( 雪橇 ). Riding a snowmobile( 雪地摩托 ) is a more m (7), but expensive way of getting around on snow. In desert( 沙漠 ) like the Sahara in North Africa, people s (8) get around on camels. Camels survive w (9) in the desert, not because they can s (10) water in their bodies though! They can survive without water for two weeks and without f (11) for up to a month. H (12) can only go without water for about three to five days. 第7空___________?