全部载荷均由底架来承担的车体结构称为（）承载结构。
A.共同
B.底架
C.整体
D.侧梁
参考答案：B
Only when _____ to explain ____ the reason for this. [ ]
A. did he start; she realized
B. he started; did she realize
C. did he start; she had realized
D. he started; had she realized
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