Are you able to solve this?

Are you able to solve this?

There's anyone can explain me the question below?
I am not so advanced with jquery at moment.
Thanks for any comment.

Which value var a should have to produce a true alert and where a variable should be:
var a = ?;
(function(a){
if(a)

function b(){alert(true)}

else
function b(){alert(false)}
return b
})(a?)(a?);