图示圆轴,固定端外圆上y=0点(图中A点)的单元体的应力状态是:()
A.A
B.B
C.C
D.D
参考答案:B
English 900 is a typical example of textbooks which provide materials for teaching and learning adopting ______ Method.
A.Grammar-Translation
B.Audiolingual
C.Direct
D.Situational
试述各种清孔方法的特点和适用条件。