Given the algorithm:

A$($n$,$x$)$

$\{$if n$==1$

return x;

else return A$($n$/2,$x$)*$A$($n$/2,$x$)$; $\}$

Its order of growth is

$*$

$\backslash$Theta $(2^$n$)$

$\backslash$Theta $($lgn$)$

$\backslash$Theta $($n$^2)$

$\backslash$Theta $($n$)$