Let f(x) = (1 + b2)x2 + 2bx + 1 and let m(b) be the minimum value of f(x). As b varies, the range of m(b) is
(a) [0, 1]
(b) [0, 1/2]
(c) [1/2, 1]
(d) (0, 1]
The correct option (d) (0, 1]
Explanation: