常温下，已知：4Al(s)＋3O2(g)===2Al2O3(s) ΔH1 4Fe(s)＋3O2(g)===2Fe2O3(s) ΔH2 下面关于ΔH1、ΔH2的比较正确的是( ) A．ΔH1>ΔH2 B．ΔH1<ΔH2 C．ΔH1＝ΔH2 D．
读经纬网和晨昏线图，阴影表示夜半球，回答问题。 α角的变化幅度大小为（ ） A．0° B．23°26′ C．66°34′ D．46°52′
地壳中含量最多的元素是 A．钙 B．氧 C．铝 D．硅
取两等份铝片，第一份与足量盐酸反应，第二份与足量烧碱溶液反应。则同温同压下放出气体的体积之比为A．1:1 B．2:3
Home shopping television networks have made _____ possible for people to shop without ever having to leave their homes. A. one B. it
读图3－27，回答下列问题。 图3－27 （1）请将城市周围的A、B、C、D四个区位合理安排花卉业、果园、乳牛业、粮食或经济作物的生产：A
如下图所示，质量为m的重锤从高h处自由下落，打在质量为M的木桩上，重锤与木桩一起下沉距离s.求木桩在下沉过程中遇到的平均阻力.
_____ the danger from the enemy action, people had to deal with a severe shortage of food, clothing, fuel and almost everything. A．As soon as B．As long as C．As far as D．As w
