A-A+
A considerable amount of time and money has be
问题详情
A considerable amount of time and money has been invested in_____this system.
A．defining
B．implying
C．reducing
D．perfecting请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：D
解析：各项的意思是：define“定义，详细说明”；imply“暗示，意味”；reduce“减少，缩小，简化”；perfect“完善，修改，使熟练”。空格处的意思是：完善这个系统。
