引起外因火灾的火源有：明火、（）、摩擦火、（）和瓦斯煤尘爆炸。
参考答案：放炮火花；机电火花
_______what they have achieved in the past five years, we still have to long way to go. [ ]
A. Comparing with
B. Compared with
C. Comparing to
D. Compare to
丙烯制冷压缩机驱动透平10-DST-501轴位移超高联锁值是（）。
A.±0.3mm
B.±0.4mm
C.±0.5mm
D.±0.6mm
