药皮的作用是保证焊缝金属获得具有合乎（）的化学成分和机械性能，并使焊条具有良好的（）工艺性能。
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In order to communicate the threat at a port facility or for a ship, the Contracting Government will set the appropriate security levels Security level 1 corresponds to（）
A. normal situations
B. medium situations
C. high threat situations
D. special situatio
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