电子管计算机统称为第一代电子计算机；（）为第二代电子计算机；第三代电子计算机是_集成电路计算机_；第四代电子计算机是大规模集成电路计算机；第五代电子计算机则是用超大规模集成电路装备的具有人工智能的巨型计算机和（）。

It was now clear that no such weapons were manufactured and none been found.

A. was found



B. were founded
C. has been found


D. have been founded