钢筋混凝土结构按承载能力极限状态计算是以（）为基础的。
A.弹性理论
B.塑性理论
C.弹塑性理论
D.刚性理论
参考答案：C
__ his telephone number or e-mail address, she had some difficulty getting in touch with John.
A．Not knowing
B．Not to know
C．Not known
D．Not having known
以下不属于社会医学主要研究内容的是（）
A.社会卫生策略
B.社会卫生状况
C.医学治疗技术
D.影响人群健康的社会因素
E.社会卫生措施
