填空题 Directions:
Read the following text and answer questions by deciding each of the statements after the text is True or False. Choose T if the statement is true or F if the statement is not true.

As an eagle wheels overhead against a crystalline blue sky, Martin Flanagan walks toward a grove of towering cottonwood trees beside the Yellowstone River, which is the color of chocolate milk due to the spring rain.
As Mr. Flanagan leaves the glaring sun of the prairie and enters the shady grove, his eyes search for specific tree. As he reaches a narrow-leaf cottonwood, a towering giant, he cranes his neck to look at the top, "This is the one I plan to nominate for state champion," he says, petting the bark with his hand. "It"s a beauty, isn"t it?"
When Europeans first came to North America, one of the largest primeval forests in the world covered much of the continent. Experts say a squirrel could have traveled from the Atlantic coast to the Mississippi River without touching the ground. But only about 3 percent of America"s native old-growth forest remains, and many of the trees they hold are those that were not big enough to attract a logger"s eye. The result is a generation of trees that barely resemble the native forests that once covered the country.
That makes some scientists suspect that the surviving forests have lost much of their genetic quality, the molecular muscle that made them dominate the landscape. When the loggers swept through, these scientists say, only poor specimens were left to reproduce. Other researchers wonder whether environmental factors or just plain luck may explain a good part of the supertrees" success.
To answer those questions, the mightiest trees of their types, or genetically identical offspring, must be preserved for study, and that is what is being done by a handful of enthusiasts, including Mr. Flanagan and David Milarch, a nurseryman Copemish, Michigan. They are searching out the largest tree of each species and taking cuttings of new growth to make copies of genetic clones of the giants. With tissue culture and grafting, they have reproduced 52 of the 827 living giants and are planting the offspring in what they call "living libraries." More than 20,000 offspring have been planted.
The work is part of the Champion Tree Project, which began in 1996 with financial help from the National Tree Trust, a nonprofit group in Washington.
"Those big trees are the last links to the boreal forests," Mr. Milarch, president of the Champion Tree Project, said.
State and federal agencies and private organizations have been keeping track of the largest trees in each state for some time. The largest effort is the National Register of Big Trees, run by American Forests, a 125-year-old nonprofit group based in Washington. But the Champion Tree Project takes things a step further by making it possible for the largest trees to live on.
Eventually the Champion Tree Project hopes to reproduce enough genetically superior trees for a nationwide reforestation project. The offspring of the native trees, should they prove genetically superior, could be especially valuable in urban settings, where the average tree lives just 7 to 10 years. But things like soil conditions, moisture and other environmental factors can also affect the success of the trees.

判断题 Water in the Yellowstone River turned dark brown because of the spring rain.

判断题 The cottonwood tree Mr. Flanagan found was an extremely tall tree with broad leaves.

判断题 In the days when Europeans first came to America, it had one of the largest primeval forests in the world.

判断题 Some scientists have the suspicion that the surviving forests have lost much of their genetic quality because they were the offspring of poor specimens.

判断题 The offspring of the supertrees have proved to be genetically superior to those of the average trees.