老年人体内蛋白质的合成能力差，同时对蛋白质的吸收利用率下降，容易出现（）氮平衡。
参考答案：负
进行全口义齿修复，患者微笑时，上唇微笑线到平面的直线距离约为上中切牙的()
A．切1/3长
B．切2/3长
C．中1/3长
D．中2/3长
E．颈1/3长
-- Do you still remember when you first met John?
--- I can’t quite remember, but I’m sure it was ______ Friday afternoon because we were at ______ school for a meeting.
A．/; the
B．the; /
C．a; /
D．/;a
