可保留的牙齿其牙槽骨吸收不能超过根长的（）
A.1／5
B.1／4
C.1／3
D.1／2
E.2／3
参考答案：E
The woman newsreader has gone to live abroad. She won't appear on TV ______. [ ]
A. any more
B. any longer
C. for longer
D. after some time
引起食物中毒的致病物质是
A．血浆凝固酶B．肠毒素C．溶血毒素D．致热外毒素E．M蛋白
