下面哪个属于皮肤的保护功能（）
A.弹性
B.水分
C.机械性刺激
D.皮脂膜
参考答案：D
We will celebrate the 90th birthday of the Chinese Communist Party _______ June 29th, 2011 in Qinzhou. [ ]
A. on
B. at
C. in
D. during
血浆蛋白如何分类？
