It is discovered by Henry Amerson's team that ______. A.southern pines cannot resist fungus B.all southern pines are not susceptible C.the genetic marker in southern pines was the easiest to identify D.fungus-resistant genes came originally from outside the U.S.A.
A.A.southern B.all C.the D.fungus-resistant
【参考答案】
B 解析：B是一个半否定的句式，因此本题关键在于理解B的All…are not…结构在意义上等同于第3段倒数第3......