如何实现存储空间的分配和回收取决于对______的管理方法。
参考答案：空闲块
a、b、c、d、e五种化合物，它们的水溶液相互反应关系如下：
①a+b→c+H2O ②c+H2SO4→d+a ③e+AgNO3→AgCl+c，
则a、b、c、d、e的化学式分别是_____ ____．
It is the film _______ director is Steven Spielberg _______ attracts quite a few viewers throughout the world.
A．that; who
B．which; that
C．whose; that
D．whose; who
