生产中对焊接残余变形矫正的方法主要有（）和（）两种。
参考答案：机械矫正；火焰矫正
心肌细胞的慢通道可被何种药物阻断
A．河豚毒
B．四乙基铵
C．Mg+
D．Ba2+
E．异搏定
To keep Chinese economy going on, the government has established an employment service system for ____ jobless urban residents.
A．badly off
B．well off
C．cut off
D．paid off
