单项选择题 若某二叉树的先序遍历序列和中序遍历序列分别为PBECD、BEPCD，则该二叉树的后序遍历序列为（）。

单项选择题 Computer （）is a complex consisting of two or more connected computing units，it is used for the purpose of data communication and resource sharing.

单项选择题 GIF files are limited to a maximum of 8 bits/pixel，it simply means that no more than 256 colors are allowed in（）.