孔隙
参考答案:
松散介质中颗粒或颗粒集合体之间呈小孔状。
It was the first time that I _______ visitors since I’d moved to London.
A.had had
B.have had
C.have
D.had
外出服务时,当服务员布置和检查完房间以后,()要再一次对房间进行全面、认真的检查。
A.服务员
B.客人
C.主管人员
D.饭店领导