【名词&注释】
对称性(symmetry)、电磁波(electromagnetic wave)、软组织(soft tissue)、声阻抗(acoustic impedance)、右心室(right ventricle)、肺动脉瓣(pulmonary valve)、肺动脉干(pulmonary trunk)
[单选题]关于肺动脉瓣(pulmonary valve)描述正确的是
A. 肺动脉瓣(pulmonary valve)位于肺动脉干(pulmonary trunk)与肺动脉漏斗之间
B. 分为两个瓣
C. 肺动脉瓣(pulmonary valve)在右心室舒张时开放
D. 肺动脉瓣(pulmonary valve)位于主动脉瓣的左下方
E. 肺动脉瓣(pulmonary valve)收缩期最大峰值流速约60~150cm/s