综合短文填空，选择正确单词填入相应的空格.

    People never travel as often as today in China. In the past, few people could travel on ____ to other countries. But today more and more Chinese people travel ____they now are becoming richer and have enough money for travel. The special plane for tourists ____ travel____ expensive than ever before. Most people enjoy ____ countries that are different from ____own. They also like to meet people and eat new food. Tourism causes many____  in Chinese people’s lives. People build new hotels and ____some people____ interesting places to ____ . Now Tourism is a big business.

比较北方地区和南方地区的自然、人文差异，将各相应的序号分别填入表格中：（填序号）

A．低于0℃              B．高于0℃ 

C．低于800m           D．高于800mm

E．平原、高原          F．平原、丘陵、高原、盆地

G．小                     H．大

I．旱地                   J．水田

鸡的卵在体内受精后就开始发育，但鸡卵产出后就停止发育，原因是（    ）