应急照明应选用（）的光源。
A.钠灯型
B.能持续发光
C.照度值大
D.能快速启辉
参考答案：D
He was so nervous during the test. No ________he didn’t pass the exam.
A．way
B．surprise
C．wonder
D．matter
配制pH=7的缓冲溶液，应选用：
