运用always 块设计一个八路数据选择器。要求：每路输入数据与输出数据均为4 位2进制数，当选择开关(至少3 位)或输入数据发生变化时，输出数据也相应地变-always use a block design options for the Eighth Route Army data. Requirements : every road input data and output data are four two-band number, When choosing to switch (at least three), or changes in the input data, output data corresponding to the change