Identify the constant time operation.

Group of answer choices

while $($x $>$ y$)$

x $=$ x $+1$

x $=$ array$[$option$]$

temp $=$ array$[$option $+1]$

for $($i $=0$; i $<$ length; i$++)$

sum $+=$ i

string str$1$

string str$2$

string str$3=$ concat$($str$1,$ str$2)$