选择精基准时，选用加工表面的设计基准为定位基准，称为（）原则。
参考答案：基准重合
什么是项目管理，怎么理解这一概念？它与一般管理有何不同？
When I talked with my grandma on the phone, she sounded weak, but by the time we()up, her voice had been full of life.
A. were hanging
B. had hung
C. hung
D. would hang
