阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。
A field trip is a journey by a group of people to a place away from ____（they）normal environment.
The purpose of the trip is usually observation for ____(educate), non-experimental research or to provide students with experiences outside their everyday ____(activity), such as going ____(camp) with their teachers and classmates. The aim of this research is to observe the subject in its natural state and ____(possible) collect samples(标本). In western culture people first come across this method during school years ____classes are taken on school trips to visit a geographical feature of the landscape. Much of the early research into the natural sciences ____(be) of this form. Charles Darwin is considered to be ____important example of someone who has contributed ____science through the use of field trips.
____(reduce) risks and expenses, most school systems now have set up field trip procedures that consider the entire trip from estimation, approval to scheduling.
