$6.$ What is the time complexity of the following function $?$

Def linear $\_$ search $($arr$,$ target$)$ :

For num in arr :

If num $==$target :

Return true

Return false

Select one :

a$.$ O$($n$)$

b$.$ O$($n$2)$

c$.$ O$(2$n$)$

d$.$ O$($Logn$)$