An array $X$ of n distinct integers is interpreted as a complete binary tree. The index of the first element of the array is $0$. If the root node is at level $0$, the level of element $X[i]$, $i \neq 0$, is
- $\left \lfloor \log _2 i \right \rfloor$
- $\left \lceil \log _2 (i+1)\right \rceil$
- $\left \lfloor \log _2 (i+1) \right \rfloor$
- $\left \lceil \log _2 i \right \rceil$