18.Computers are becoming faster, more powerful,and more reliable,and (so too are modems, they are the devices to allow )two or more computers to share informations over regular telephone lines.

A. so too are modems, they are the devices to allow

B.so too are modems, the devices that allow

c.so too modems, the devices allowing

d.also modems, they are the devices taht allow

e,also modems, which are the devices to allow答案为什么不选e而选b呢?多谢!