普通混凝土空心砌块的试验项目有（）
A.抗压强度
B.空心率
C.坚固性
D.抗冻性
E.抗渗性
参考答案：A, B, D, E
In general,a typical （）model is composed ofseveral phases, such as requirements analysis phase, general/detailed design phase, implementation phase, system acceptancetesting phase.
A．waterfall
B．incremental
C．spiral
D．prototyping
何谓气滞、气逆、气陷、气闭、气脱其病因及病机变化的特点是什么
