经肘静脉注入对比剂,最先显影的是()
A.上腔静脉
B.肺动脉
C.主动脉
D.肾动脉
E.门静脉
参考答案:A
解析:根据解剖结构,经肘静脉回流无名静脉,再至上腔静脉进入右心房。
人们不能自由选择某一社会形态。
The ()view of language sees language as a linguistic system made up of various subsystems: the sound system (phonology); the discrete units of meaning produced by sound combinations (morphology); and the system of combining units of meaning for communication (syntax).