铝合金时效强化的根本原因是（）
A.细化晶粒
B.组织结构改变
C.消除内应力
D.加工硬化
参考答案：B
With the ______ of making a fortune,many people went to Australia in the 19th century to wash sand
for gold. [ ]
A. task
B. intention
C. trade
D. appointment
嫘祖 lãi zǔ
