螺纹每层加工的轴向起刀点位置可以改变。
参考答案：错
It is said that some software on learning subjects for pupils _______ in a very practical way. [ ]
A. designed
B. is designed
C. designs
D. is designing
（）种焊剂是目前国内生产中应用最多的一种焊剂。
A.粘接焊剂
B.烧结焊剂
C.熔炼焊剂
