根据下列短文内容，在短文后的空格处填上一个恰当的词，使短文完整、通顺。

     Stamp collecting is a popular    1   . I like collecting stamps. Most of my stamps are   2    France,

Canada, Russia and the USA. I know I can't    3    stamps from every country because there are too

many.

     I don't buy any stamps because they    4    too much money. My father often goes to other counties

for work, so he can    5    foreign stamps home. If I don't like a stamp, I try to change it with others.

     Most of my stamps are used (用过的)    6   . I have to get the stamps off the envelopes (信封). I put

the envelopes into a bowl of water. After a few minutes the water makes the envelopes    7   . Then it's

   8    for me to peel off (剥落) the stamps. After that, I let them dry and put them in my stamp album.

     My stamps make my school subjects interesting. They    9    me what animals, plants, mountains and

rivers there are in a country. It is helpful for my study.   10   some of my stamps will become valuable

someday.