【名词&注释】
颈动脉(carotid)、椎动脉(vertebral artery)、吸收光谱(absorption spectrum)、头颈部(head and neck)、辐射量(radiation quantity)、扫描时间(scanning time)、明显提高(improved obviously)
[单选题]红外激光片(IR型)的吸收光谱峰值为
A. 520nm B. 620nm C. 720nm D. 820nm E. 920nm