We were having a meeting ______ suddenly someone knocked at the door. [ ]

A. because

B. when

C. as

D. while

脑内肿瘤诊断的CT定位征象是()

A．肿瘤边缘多不清楚

B．与颅内板呈钝角

C．易引起骨质改变

D．局部蛛网膜下腔增宽

E．脑皮层位置移位