She's never seen such a good film, ____ she? [ ]
A. is
B. isn't
C. has
答案：C
焊缝和热影响区性能最好的焊接方法是______。
A．气焊
B．焊条电弧焊
C．埋弧自动焊
D．手工钨极氩弧焊
体育锻炼对心血管系统有哪些良好的影响。
