绘图题:画出德士古煤炭气化工艺流程。
参考答案:
Helen and Mary are good friends. _______ often help each other. [ ]
A. Them
B. Theirs
C. They
D. Their
铁路合同包括______。
A.旅客车票
B.行李票
C.包裹票
D.站台票