经腹扫查，妊娠几周可显示妊娠囊结构（）。 A.2~3周 B.7~8周 C.5~6周

Once the foreign friends are _____ with the Chinese words, they can understand the books easily. [ ]

A. familiar

B. occupied

C. similar

D. special

It was not until mid-night_______ they reached the camp site.

A．that

B．when

C．while

D．before

肾癌常需要与下列疾病鉴别()

A．肾孤立性囊肿

B．肾结核

C．多囊肾

D．肾积水

E．输尿管肿瘤

把病弱儿童列为特殊教育的对象的国家（或地区）是（）。

A.中国

B.越南

C.日、美等国家

D.中国台湾

简述谈判现场不布置谈判桌的益处。