长期合同采购的供需关系（），主要适用于采购方需求量大、需求连续不断的情况。
参考答案：稳定
_____ a written permission, he had to write another letter to the president of the university. [ ]
A. Not giving
B. Not having been given
C. Having not given
D. Having not been given
下列哪项在梗阻性黄疸的鉴别中意义不大()
A．胆管及胰管扩张程度
B．胆管及胰管扩张平面
C．胆管形态及管壁厚度
D．肝脏大小及密度
E．有无结石和软组织肿块
