CT扫描前不做空气校准，会造成：

A．采集数据的准确性下降

B．工作效率提高

C．机器工作稳定

D．图像质量得到保证

E．节省球管，延长寿命

When Christine landed her job some years ago, she had to face a climate _____ music classes were not

the focus of learning. [ ]

A. which

B. where

C. when

D. that