货车底架主要由哪些部件组成？
参考答案：
中梁、侧梁、牵引梁等纵向梁，枕梁、端梁、大小横梁等横向梁。
I want ____ the answer to the problem. Could you help me? [ ]
A. to come up with
B. coming up with
C. come up with
D. came up with
现场总线设备的工作电压在（）。
A、24V
B、9-32V
C、12-24V
D、5-32VV
