多数树种的木材纤维饱和点的含水率平均值为（）。
A.30%左右
B.20%左右
C.40%左右
D.25%左右
参考答案：A
Which of the following most accurately describes the passage
A．(A) A description of a replicable experiment
B．(B) A summary report of new findings
C．(C) A recommendation for pursuing a new area of research
D．(D) A refutation of an earlier hypothesis
E．(E) A confirmation of an earlier research
分组密码算法的设计思想是由C.E.Shannon提出的，主要通过（）来实现。
