Which statement about the following JavaScript code is true?

greeting $+=$ Youareacutelittlekid.:

greeting $+=$ "You are old enough to drive.";

$\}$ else $\{$

greeting $+=$ "You are over the hill!"

a$.$ The else branch is unnecessary because the preceding branches already covered all possible conditions.

b$.$ The second inlsin if branch $[$beginning inlsin if $($ aginAtB irthday $==16)]$ will nerel execute. even if ageAtBirthday equals $16.$

d$.$ This code will cause a runtime emror because the curly braces are not positioned correctly.