A. only occurs beneath the surface of a metal or alloy B. can lead to weakening of the metal or alloy C. prevents liberation of elements from the metal or alloy D. A and B
A. combining it with citric acid B. adding a grain refmer C. cooling the molten metal slowly D. copper,osmium,and iridium
A. 缩聚反应 B. 自由基聚合反应 C. 加聚反应 D. 以上都不是