若过去用药已发生过敏,再次用该药时一般多久发生变态反应
A.10min
B.10h
C.4~20d
D.1d
E.3~5d
参考答案:B
Telephone users sometimes complain about unreliable service and they consider unfair charges.
A.which
B.that
C.what
D.how
离子交换反应的条件是什么?