Code example $13-2$

public class CustomerList

$\{$

private List customers;

public delegate void ChangeHandler$($CustomerList customers$)$;

public event ChangeHandler ChangedList;

public CustomerList$()$

$\{$

customers $=$ new List$()$;

$\}$

public void Add$($Customer c$)$

$\{$

customers.Add$($c$)$;

$\}$

public static CustomerList operator $+($CustomerList customers, Customer c$)$

$\{$

customers.Add$($c$)$;

return customers;

$\}$

$\}$

$($Refer to code example $13-2)$ Which of the following statements activates the event that$$s declared for the CustomerList class?

Group of answer choices

if $($ChangedList $!=$ null$)$ ChangedList$($this$)$;

if $($ChangedList $==$ null$)$ ChangedList$($this$)$;

if $($ChangedHandler $!=$ null$)$ ChangedHandler$($this$)$;

if $($ChangedHandler $==$ null$)$ ChangedHandler$($this$)$;