# Is a subset of $\mathbb{R}^{n}$ that is homeomorphic to $\mathbb{R}^{n}$ necessarily open? [duplicate]

Let $A$ be a subset of $\mathbb{R}^{n}$, such that $A$ is homeomorphic to $\mathbb{R}^{n}$.

Is $A$ open in $\mathbb{R}^{n}$?

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