A:镀铜铁制品不可以在弱酸性条件下使用
B:镀铜铁制容器可盛硝酸银溶液
C:镀铜铁制品不易生锈的原因之一是使铁隔绝了空气
D:镀铜铁制品是一种合金
设变量x,y满足约束条件x≤2y≤xx+y≥2则目标函数z=2x+y的最小值为( )
完型填空
1 is an American girl. 2 name is Helen. And this is Mike. 3 is an English boy. Mike can 4 his name. Kate can sing ABC song. Mike's home phone number is 658-4323. He can5Kate at 954-3643. They6friends now.