题干
The factory ______ last year was equipped with the latest machinery.
A：which I worked
B：in which I worked
C：of which I worked
D：where I worked i
答案(点此获取答案解析）
B
的匀强磁场，
轴下方存在垂直纸面向外的磁感应强度为
角斜向上射人磁场，且在上方运动半径为R，不计重力。则（ ）