Let $$f : R \to R$$ be a function such that $$f(x) = \frac{x^2+2x+1}{x^2+1}$$. Then

A

$$f(x)$$ is many-one in $$(-\infty, -1)$$

B

$$f(x)$$ is many-one in $$(1, \infty)$$

C

$$f(x)$$ is one-one in $$[1, \infty)$$ but not in $$(-\infty, \infty)$$

D

$$f(x)$$ is one-one in $$(-\infty, \infty)$$