电脑操作员眼晴距显示器屏幕的距离多远为安全?
参考答案:
30~60厘米。
—Where did you go last night?
-I _______to go to Lily’s birthday party.
A.have been asked
B.have asked
C.asked
D.was asked
衡量医院感染的常用指标不包括()
A.发病率
B.患病率
C.漏报率
D.时点患病率
E.比值比