从石器、青铜器到铁器时代，金属的冶炼体现了人类文明的发展水平。下图表示了三种金属被人类开发利用的大致年限，之所以有先后，主要取决于A.金
对于锌、铜和稀硫酸组成的原电池（如图），下列有关说法正确的是 ①Zn是负极 ②电子由Zn经外电路流向Cu③Zn -2e-=Zn2+
____ different kinds of pianos, the workers farther improved their quality A. To produce B. Being produced C. Produced D. Having produced
在河南省境内通过的铁路线有（ ） A．京广线、陇海线、焦柳线 B．京九线、京沪线、京广线 C．浙赣线、哈大线、京广线
某人后脑部位受损，心跳和呼吸立即停止并死亡，受损部位可能是 （ ）A．小脑 B．躯体运动中枢 C．脑干 D
Tim will call me as soon as he __________ my package. A．receive B．will receive C．received D．receives
Christmas is the most important festival in the western world. It 76 (fall) on December 25th. When my mother and I stayed in America, we 77 (invite) by one of my mother’s frie
My father has a computer, but he doesn’t know to use it. A. what B. how C. who D. which
