根据题意得：x-4＞0，解得x＞4．
下列那种离子对降低血管通透性和神经兴奋性的作用，可以减轻过敏反应，是UV脱敏的机制（）
A.Na+
B.K+
C.Mg2+
D.Ca2+
Japan occupied Korea for 35 years, and many Koreans still harbor very bitter memories of that time, a time when they were prevented from speaking their own language and had to pledge allegiance to the Japanese emperor.
