I can’t remember when I started collecting litter. But it was when I got tired of   46  litter nearby that I realized no one else was going to pick it up.
I live near a forest in Ohio, America. I can walk there   47  three minutes. I used to love going there to play with my dog. But one day there was   48  much litter there that I became very unhappy. I decided to clean up the forest, and I wanted to   49  happy when I went again. I made my first trip to clean the forest that afternoon. I took a big black rubbish bag with me. Ten minutes   50  I started to pick up litter, my bag was full! There were cans, bottles, broken glass and newspapers in it.
From then on, I  51  to the forest four times a year to pick up litter. I often stay there for three hours. It makes me feel   52  to do something for the environment. After each trip, I look through all the litter that I’ve collected. If   53  of it is recyclable（可回收利用的）, I’ll keep it. I can’t understand why people drop litter. But I will keep on picking it up   54  they stop dropping it.. I know I am only doing a small bit   55  the earth, but I still think it is important.
A.seeing           B.throwing          C.dropping         
A.after            B.for               C.in
A.such         B.very              C.so                   
A.make         B.feel              C.look             
A.after            B.later             C.before               
A.had gone     B.have gone         C.go               
A.tired            B.sad               C.great
A.many         B.few               C.any      
A.until            B.after             C.as soon as           
A.helped          B.to help               C.help