While on a family canoe trip on the Fox River a few years ago, Grant and Colton Shepard were disturbed by what they saw in the water. " We were there to enjoy the     ，" says Grant，11，"    —we saw a lot of litter (垃圾）. "
The brothers, who live in Riverside, Illinois, went home and took action. They      the Illinois Department of Natural Re-sources，   to monitor local rivers and streams carefully. They     training workshops to become familiar with the organisms(微生物）that are found in local    .
Ever since, the two boys have been taking weekly      from two rivers. They study them to make certain that the underwater ecosystem is      . Sometimes they find strange things. "We     discovered a big picnic table that had     underwater ！ " says Grant.
It's not just rivers that these kid volunteers     . They have devoted themselves to keeping their environment   12  balanced. "In the future, we're going to need more resources.     we protect them now, they won't be there for us. "says Colton，14.
Every year，   their campaign for a cleaner world, the brothers         at least 100 days without using a car. Their purpose is to cut down on the        gases that cars give off into the air. The brothers have also been active in helping    Illinois' precious grassland. For the past two years, they have spent     one Saturday a month clearing away non-native plants from a100-acre rare oak (橡木)grassland. " The plants and bushes      our heritage because they prevent the old oaks from growing    ，" says Grant.
A. garden       B. grass       C. beauty      D. trip
A. because      B. so         C. though       D. but
A. contacted    B. reminded    C. informed     D. interviewed
A. preparing    B. offering    C. advising     D. agreeing
A. produced     B. provided    C. attended     D. held
A. forests      B, lakes      C. waters       D. schools
A. wastes       B. samples     C. polluters    D. liquids
A. in order     B. in place    C. in danger    D. in balance
A. never        B. often      C. once         D. seldom
A. put          B. deserted    C. sunk         D. left
A. pick out     B. care about  C. look out     D. take over
A. slightly     B. regularly   C. totally      D. finally
A. Even if      B. As long as  C. Before       D. Unless
A. for the purpose of  B. as a result of  
C. as part of    D. as well as
A. walk         B. run        C. choose       D. go
A. extra        B. harmful    C. useless      D. various
A. decorate     B. plough     C. design       D. restore
A. at least     B. in turn    C. as usual     D. at most
A. destroy      B. threaten    C. change       D. replace
A. rightly      B. nicely     C. properly     D. separately