前馈调节系统，是指根据（）进行调节而不测量被调量的自动调节系统。
参考答案：扰动
I became a student ten years . I have been a student 1996. I have studied here_____ about 10 years.
A. ago, since, for B. ago ,for ,since, C. ago, before, for D ago, in, after
