Prevent execution of parent event handler

Answer 1

use

event.stopPropagation()

Stops the bubbling of an event to parent elements, preventing any parent handlers from being notified of the event.

when click on b and c

Answer 2

You can add a handler for the child that will prevent the click event from propagating up:

function handler(event) {
    event.stopPropagation();
    // now do your stuff        
}
$('#a').add('#b').click(handler);

This way clicks to '#b' will not propagate to '#a'. Neither will clicks to '#c' go to '#b', and hence not to '#a'.