钢筋现场代换的原则有（）
A、等面积代换
B、等应力代换
C、等长度代换
D、等强度代换
E、等根数代换
参考答案：A, D
简述poly(A)与翻译效率的关系。
He was elected ______ president of the company, and _____ news came , in fact, as ______ surprise. [ ]
A. a; the ; /
B. /; the ; a
C. a; /; the
D. the; the; a
