The graph of f(x) is increasing on
(-∞, 0) and decreasing on (0, +∞).
Which statement must be true?
A f(x) has a maximum at x = 0.
B f(x) has a minimum at x = 0.
The domain of f(x) is (0, +∞).
D The range of f(x) is (0, +∞).