Martin and his friends didn't eat up all the food they ordered, ______ they took the rest away.      [ ]

A. for          

B. or              

C. so                

D. as

拔上颌第一磨牙腭侧断根时，牙根阻力突然消失，拔牙窝空虚，捏鼻鼓气时拔牙窝无气体溢出，可能为()

A．牙根进入腭部黏膜下

B．牙根进入鼻腔黏膜上

C．牙根进入上颌窦

D．牙根进入上颌窦黏膜下

E．牙根进入颊侧黏膜下