A.對(duì)鋼質(zhì)活塞可實(shí)行焊補(bǔ),但需預(yù)熱和退火B.鋁質(zhì)活塞發(fā)現(xiàn)裂紋應(yīng)更換C.航行中,若無(wú)備件,則需減缸航行D.對(duì)鋁質(zhì)活塞也可實(shí)行焊補(bǔ),且無(wú)需預(yù)熱和退火