金属矿石按所含金属矿物性质，矿物组成或化学成分可分为哪几类？
参考答案：
金属矿石分为：自然金属矿石、氧化矿石、硫化矿石、混合矿石。
A (71) is a data type whose major attributes are determined by the rules governing the insertion and deletion of its elements. The only element that can be deleted or removed is the one that was inserted most (72) . Such a structure is said to have a last-in/first-out (LIFO) behavior, or protocol.
A．stack
B．queues
C．pointer
D．record
对反动式汽轮机而言，蒸汽在喷嘴中（）压力降，在动叶中（）压力降。
