in 的用法和关于in 的词组

1 介词：在...里,如：in the bag； 用于某些时间名词前,如：in the morning
在...后,表示将来,如：in two hours
2 副词：在家 be in=be at home
in class
in English-speaking countries
have some problems ( in ) doing sth.
put sth.in order
an e-mail from Lucy to her friend in the USA
in the open air
in the country
in the fields
in the city
in summer
be with sb.in s.p.for the summer
the animals in cages
in forests
fall in the water
in front of …
in the back row
in the middle of …
in the center of …
stand in a row
in front of the class
put one’s hands in front of sb.