Young people should travel not only to find out about the present 31           to find out about the future. A grand tour today should be the opposite of 32          it was in the past. It should not include museums, castles and ruins. It should go       33           human life is, to places that throw you images of the future. It should not be an escape of 34            (real) but a challenge with 35           .

Young people of today should go to the wildest, farthest, poor place they can think of. They should go to the wild places of Asia, Africa, and South America. Young people should go to 36         many such places as they can, 37           these places are closing up and in time they’ll become impossible.

The other area young people should travel 38  ____________  is the same sort of area within their own country, places that are a kind of 39  ____________  (know) land, 40   _______  as the Congo Basin.

固定义齿修复的生理基础不包括（）

A．牙周潜力

B．基牙牙髓活力

C．牙周膜面积

D．牙槽骨结构

E．牙槽骨高度