由于腐蚀介质中去极化剂的存在，使得单-金属不能够与腐蚀介质构成腐蚀电池。
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Listen to the passage Why Do We Study English and tick the reasons for studying English mentioned by the speaker.[音频]
A. It is one of the most widely used languages in the world.
B. It is the language spoken by the largest population.
C. It is the only official language of the U.S.
D. It is one of the working languages at international meetings.
E. 80% of commercial emails are written in English.
F. It is the only official language used in the U.N.
G. Millions of books and magazines are written in English.
H. It is really a bridge to knowledge.
It enables us to visit foreign websites.
J. It helps us learn modern science.
阅读代码并填空：int[][] arr=new int[2][3];for(int i=0;i<2;i++){for(int j=0;j<3;j++){arr[i][j]=i+j;}}1)arr的元素个数是（）2)下标1(行下标)的最大值是（）3)下标2(列下标)的最大值是（）4)arr[1][2]的值是（）
葡萄糖顺浓度梯度跨膜转运依赖于细胞膜上的
A. 脂质分双分子
B. 紧密连接
C. 通道蛋白
D. 载体蛋白
E. 钠泵
关于Na +泵生理作用的描述不正确的是
A. Na+泵活动使膜内外Na+、k+呈均匀分布
B. 将Na+移出膜外,将K+移入膜内
C. 建立势能储备,为某些营养物质吸收创造条件
D. 细胞外高Na+可维持细胞内外正常渗透压
E. 细胞内高K+保证许多细胞代谢反应进行
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