Hi Harish,
Here checkbox is expecting the boolean value but it is bind with String so it is giving error.
You can try to do dynamic binding for the same. For this complex binding should be set to true at component.js or index.html wherever your bootstrapping is done.
For example
checkbox.bindProperty("checked","fieldname", function(fieldname){
if(fieldname=="A")
return true;
else
return false;
});
There is also error for controller reference. You have to fix that too.
With Regards,
Ramesh Shrestha