位于椎管前壁的韧带是
A．前纵韧带B．后纵韧带C．棘上韧带D．黄韧带E．项韧带
参考答案：B
垄断组织在购买生产资料时规定的价格是（ ）
A．垄断高价
B．垄断低价
C．自由价格
D．保护价格
So absorbed ________ in the research that she didn’t hear someone knocking at the door.
A．she did
B．did she
C．she was
D．was she
