肺空腔
参考答案：是由肺内腔隙呈病理性扩大所致，如肺大泡、肺气囊和含气的肺囊肿。
His poor _____ English prevented him _____.
A．spoken; from understanding
B．spoken; from being understood
C．speaking; from understanding
D．speaking; from being understood
防止远中游离端义齿撬动的卡环是
A．回力卡环B．圈形卡环C．长臂卡环D．对半卡环E．BPI卡环
