单选题When first ________ to&nb

问题补充：

单选题Whenfirst________tothemarket,thecomputersoftware．wasnotasuccessduetoitscomplexityinoperation.A.introducingB.being introducedC.introducedD.to be introduced

答案：

C解析状语从句的省略 ， 完整的从句为 ： When it was first introduced.