裂纹是指金属的连续性被破坏而形成的缺陷。
参考答案:对
北伐战争期间,上海工人发动的第三次武装起义()
A.推动了五卅运动的发展
B.声援了省港大罢工
C.成功收回了上海英租界
D.配合了北伐军进驻上海
Science and technology __________ nowadays in our socialist construction.
A.plays an important part
B.play an important part
C.play important parts
D.take important parts