# Big-O notation basic

One day your friend who has a tendency of lying on pretty much everything came up to you made the following three claims:

\begin{aligned} &(A) &\quad (n+k)^{ x }\quad &=&O(n^{ x }) \\ &(B) &\quad 2^{ 2n+1 }\quad &=&O(2^{ n }) \\ &(C)& \quad{ 2 }^{ n+1 }\quad &=&O({ 2 }^{ n }) \end{aligned}

For constant $k$ and $x$, which of the statements is actually true?

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