What is the best$-$case runtime of Insertion sort?

Note: The symbol $^$ means power. E$.$g$.,2^$n $=2$n

Group of answer choices

T$($n$)=$ O$($log n$)$

T$($n$)=$ O$($n$)$

T$($n$)=$ O$($n log n$)$

T$($n$)=$ O$($n$^2)$

T$($n$)=$ O$(2^$n$)$