单项选择题

Text Men have traveled ever since they flint appeared on earth. In primitive times they did not travel for pleasure but to (26) new places where their herds could feed, or to escape from (27) neighbors, or to find more (28) climates. They traveled on foot. Their (29) were long, tiring and often dangerous. They protected themselves with simple (30) such as wooden sticks or stone clubs, and by lighting fires at night and, (31) all, by keeping together. Being intelligent and creative, they soon (32) easier ways of traveling. They (33) on the backs of their domestic animals; they hollowed out tree (34) and, by using bits of wood as paddles, were able to travel (35) water. Later they traveled, not from necessity, but (36) the joy and excitement of seeing and experiencing new things, which is still the main (37) why we travel today. Traveling, of course, has now become (38) organized business. There are cars and splendid roads, express train, huge ships and jet airliners, all of (39) provide us with comforts and security. This sounds wonderful. (40) there are difficulties. If you want to go (41) , you need a passport and visa, tickets, luggage, nd a hundred and one (42) things. If you lose any of them, our journey may be (43) . Scientists have invented machines that can explore (44) space. Eventually there will be cheap day journey to the moon and honeymoons on Venus. People will be able to fly from one planet to another in nasty little arrow-shaped tubes. I say "people" because I have no (45) of being one of them.