.He was about to leave ______the telephone rang; ______was from his mother.

A．when; that

B．before; which

C．when; it

D．before; this

为确定诊断，下一步选择最恰当的检查应是

A．全血常规

B．血培养

C．脑CT扫描

D．颅脑B超

E．脑脊液检查