题目

—After the 2008 Olympic Games, more and more people in western countries begin to learn Chinese _____ they can better understand the culture of China. — I’m sure they will. A. because of         B. so that     C. even though        D. as if 答案：B12．若函数f（x）=4x+a•2x+a+1在R上有且只有一个零点，则实数a的取值范围是a=2-2$\sqrt{2}$或a≤-1．