What is the most accurate running time in big$-$O of the following algorithm?

$O(n^2)$

$O(n^3)$

$O(n^4)$

$O(n^5)$

$O(nlogn)$

What is the most accurate running time in big$-$O of: $n^{\frac{1}{2}}+n+logn?$

$O(n^{\frac{1}{2}})$

$O(logn)$

$O(n)$

$O(nlogn)$