Men have travelled ever since they first appeared on the earth. In primitive times th

Men have travelled ever since they first appeared on the earth. In primitive times they did not travel for pleasure but to【C1】______ new places where their herds could feed, or to escape from hostile neighbors, or to find more【C2】______ climates. They travelled on foot. Their journeys were long, tiring, and often dangerous. They protected themselves with simple【C3】______ such as wooden sticks or stone clubs, and by lighting fires at night and, above all, by keeping together. Being intelligent and creative, they soon【C4】______ easier ways of travelling. They rode on the backs of their domesticated animals; they hollowed out tree【C5】______ and, by using bits of wood as paddles, were able to travel across water. Later they travelled, not from necessity, but【C6】______ the joy and excitement of seeing and experiencing new things, which is still the main【C7】______ why we travel today. Travelling, of course, has now become a highly organized business. There are cars and splendid roads, express trains, huge ships and jet airliners, all of【C8】______ provide us with comforts and security. This sounds wonderful. But there are difficulties. If you want to go【C9】______ , you need a passport and a visa, tickets, luggage, and a hundred and one other things. If you lose any of them, your journey may be【C10】______ .

【C1】

A．visit

B．find

C．purchase

D．explore

请帮忙给出正确答案和分析，谢谢！