修复牙列缺失时，后牙胎力应集中在
A．第二前磨牙及第一磨牙区B．第一磨牙和第二磨牙区C．第一磨牙区D．第二磨牙区E．第一、二前磨牙区
参考答案：A
The company had about 20 notebook computers but only one third _________ used regularly.
Now we have sixty working all day long.
A．is
B．are
C．was
D．were
AIDS属于哪种免疫缺陷病（）
A.原发性T细胞缺陷病
B.原发性B细胞缺陷病
C.原发性吞噬细胞缺陷病
D.原发性联合免疫缺陷病
E.获得性免疫缺陷病
