喉头的位置相当于颈椎（） A.C3 B.C4 C.C5 D.C6 E.C4～6

     Robert performs his 24-foot boat past willow(柳树) young trees that stick out of the waters of the
Mississippi River. __1__ dances off maples(枫树), their branches heavy with __2__ spring leaves. But a
 _3__ inspection discloses trouble behind the beautiful sight. Rubbish is __4__ in a logjam(浮木阻塞) and hangs from the tree's branches.
     For the next three hours Robert and his team pull plastic bags, tanks, bottles and __5__ bowling pins
out of the water. Then they __6__ for a picnic table caught in the trees. Welcome to the Mississippi River
Beautification Project begun in 1997 with Robert's one man __7__  to pick up rubbish __8__ a 400 mile
stretch(伸展) of the 2,340 mile river. That year, often working __9__, the 22-year-old fellow cleaned 150 miles of shoreline.
     At first the project appeared__10__ and useless. But Robert tried his best to find __11  , and with their backing, he soon had a new boat and five-man __12  -the Boom Crane Crew. Last year alone the crew
 __13_ from the water 44,055 gallon durms,1,104 tires and enough plastic bags to __14__  a football
field. Much of the waste will be __15__.
      "Robert's operation is the only one actually in __16___on the river," says Mark of the Mississippi
River Basin Alliance, a union of environmental groups. "It's the __17_I have ever seen in 20 years, and he
is inspiring others to do the __18_ ."
      "The river has given me a livelihood and brought me so much _19_ ," Robert says, "I want to do
something in __20_ ."