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Which of the following maps are surjections from $\mathbb{R}$ to $\mathbb{R}$? Select ALL that apply.

$f(x)=e^x$

$f(x)=x^5-2x^4+1000$

$f(x)$ is the smallest real number no larger than $x$ whose decimal expansion does not contain $7$.

$f(x)=e^x-e^{-x}$