評論
打印
Writing & Language
Some plant pathologists have turned to genetic engineering to devise new ways of responding to botanical diseases. Plant pathologist William Powell, for instance, teamed up with forest biologist Chuck Maynard to restore North America's population of American chestnut trees, which was decimated in the early 1900s by a fungus known as chestnut blight. A fungus, C. parasitica, contributes to the growth of cankers on the trees' trunks; these cankers, in turn, prevent trees from transporting water from their roots to their branches and leaves. To render American chestnut trees resistant to the blight, Powell and Maynard experimented with altering the genetic makeup of the trees. The resultant genetically engineered trees are called Darling 4 American chestnut trees, and they undergo greater increase in canker growth between weeks 10 and 15 after infection with chestnut blight than they do between weeks 1 and 5.
Which choice most effectively interprets data in the graph to provide support for the paragraph's discussion of Powell and Maynard's work?
A.NO CHANGE
B.by the 15th week after being infected with chestnut blight, they grow cankers as large as 14,000 millimeters.
C.they show signs of being immune to chestnut blight since they are not susceptible to canker growth within the first 15 weeks after exposure to the fungus.
D.during the first 15 weeks after infection with chestnut blight, they grow cankers that are much smaller than those that grow on American chestnut trees.
