阅读理解。
     People who travel long distances will have to decide whether they would prefer to go by land,
sea or air.Maybe nobody would say they enjoy sitting in a train for more than a few hours. The
train will soon get crowded and dirty. It is almost impossible to take your mind off the joumey.
Reading may help you to kill time but soon the clicking on the rails will bring you to sleep. During
the day,sleep never lasts long. At night,when you really wish to go to sleep,you find you can hardly
manage to do so. If you are lucky to get a sleeping seat,you spend half the night looking at the small
blue light over your head,and when you finally arrive at the station,you are
so tired that you don't want to leave.
     Long car joumeys are even less pleasant,for it is impossible even to read. On motorways, you
can, at least,travel fairly safely at high speeds,but more often,the greater part of the joumey is spent
on narrow,bumpy (崎岖不平的)  roads which are crowded with traffic.
     When travelling by sea,you have a different expe- rience. You can have a walk.on the board,
play games, swim,meet interesting people and enjoy good food,and of course,only when the sea is
calm. If it is not,you are likely to get seasick (晕船的) , and you will find no joumey can be worse
than that. Even if you travel in good weather,sea joumeys take a long time. Few people
would like to spend a third of their holidays for the pleasure of travelling on a ship.
      Travelling by plane seems to be dangerous to some people,and,it is also the most expensive of
all travelling forms,though nothing can match planes for speed and comfort(舒服). Flying at a height
of 30 000 feet, far above the clouds,and at 500 miles an hour is a very exciting experience. The
joumey is  so  smooth(平稳的 )that there is nothing to prevent you from reading or sleeping.
However you decide to spend your time,one thing is certain:you will arrive at your destination fresh
and easy. You will not have to spend the next few days recovering(恢复)from a long and tiring journey.
1. From the passage we can know that travelling by train              .
A.is the most comfortable for passengers
B.is so slow and dirty that no one wants to take a train
C. seems to be very tiring and usually takes a long time
D. will keep you awake all the time
2. What prevents people from travelling by plane?  
A. Planes can be very dangerous.
B. You will feel sorry after travelling by air.
C. Flying so high brings no comfori.
D. Air travelling takes a long time.

3.In the writer's opinion,             .