血清病的发病机制主要是（）
A.Ⅰ型变态反应
B.Ⅱ型变态反应
C.Ⅲ型变态反应
D.Ⅳ型变态反应
E.以上都不是
参考答案：C
Totally ________, both of the world famous writers were born and died on the same day and of the same disease. [ ]
A. by coincidence
B. by incident
C. by accident
D. by luck
若一个长方形的宽减少了20%，保持长方形的面积不变，长方形的长应增加( )%。
A．45B．20C．25D．30
