阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填人一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为16 ~ 25的相应位置上。

As a child, I was always out exploring my local area, whether swimming at the beaches or hiking through the bush. Australia’s outdoor lifestyle had me hooked on adventure and nature. I always wanted to explore   16  else was out there. Going on family holidays to many of the East Coast beach towns was always   17  fun adventure into the   18  (know). I came to love the beauty of world, and began to recognize just   19  much the planet had to offer, even   20  my experience of it was only in my backyard.

Also, Australia is very remote and detached from the rest of the world.   21  (Europe) often drive into other countries for   22   summer vacations. We never had that luxury and   international travel seemed all the more exotic and   23  (adventure) to me. Very often, we   24  (expose) to other countries through TV and movies,   25  I wanted to experience it for myself.

国界是地图上一国与          或公海之间的界线，它是国家           范围的边界。国界都是国家间经过           商定的，人为划分的。有些国家之间，以自然的            、           、湖泊为界，有些国家之间以           为界，在一定地段设立界碑、界墙、栅栏作为标志。还有一些国界，是根据历史的、             的、              的等原因来划定的。