谷胱甘肽对于紫外线降低皮肤免疫力有防御效果，对于紫外线对（）细胞进行照射时，添加谷胱甘肽比不添加谷胱甘肽的对紫外线的防御能力强1.5倍。
参考答案：郎格罕氏
From that time on Nancy practiced the piano every day.[ ]
A. plays
B. playing
C. played
D. to play
直流锅炉各参数间的关系（即动态特性）有何特点？
