Which expression for XXX causes the code to output the strings in alphabetical order? $($Assume the strings are lowercase$)$

if $($XXX$)\{$

cout $<<$ firstStr $<<""<<$ secondStr $<<$ endl;

$\}$

else $\{$

cout $<<$ secondStr $<<""<<$ firstStr $<<$ endl;

$\}$

Group of answer choices

firstStr $==$ secondStr

firstStr $>$ secondStr

firstStr $<$ secondStr

firstStr $!=$ secondStr