简述债券的一般特征。
参考答案：
解析：(1)收益性；(2)安全性；(3)流动性。
已知a、b、c满足a﹣b=8，ab+c2+16=0，求2a+b+c的值．
This computer is _______ than that one, but it works much _______. [ ]
A. expensive; fast
B. the cheaper; the fastest
C. more expensive; faster
D. the most expensive; the faster
