Our town________poor in the past, but great changes________in the town in the past three years.[ ]

A. was; had taken place  

B. was; have taken place

C. has been; had taken place  

D. has been; have taken place

粘结与下列哪个因素无关（）

A.材质

B.退火温度

C.几何尺寸

D.冷却速度