单项选择题
The result of two forces acting in opposite directions and along parallel lines，is an example of what type of stress?（）
A.Tensile B.Compression C.Shear D.Strain
单项选择题 The purpose of sheer in ship construction is to（）.
单项选择题 The procedure of strengthening damaged structures on a ship by using wood or steel is called（）.
单项选择题 The pillar shape that gives the greatest strength for the least weight is the（）.
