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Let $M^4$= $I$,(where $I$ denotes the identity matrix) and $M \neq I$, $M^2\neq I$ and $M^3\neq I$. Then,for any natural number $k$,  $M^{-1}$ equals:

1. $M^{4k+1}$
2. $M^{4k+2}$
3. $M^{4k+3}$
4. $M^{4k}$