扳道、信号人员在值班时应做到哪些？
参考答案：
扳道、信号人员在值班时应做到严格按照车站值班员的接发列车命令、调车作业计划，正确及时地准备进路。
已知3x+1和2x+4互为相反数，则x=( )
With all the things he needed _______, he went home happily.
A．bought
B．buying
C．to be bought
D．to buy
