发动机低速运转时，可变配气机构的三个摇臂（）。
参考答案：各自独立运动
A study ________ in the U.S.A. in 1977 showed that the chemical ASA in aspirin could prevent a stroke.
A. carrying out B. carried out C. working out D. worked out
电力机车防塞过冬整修范围？
