77 Given that a web application consists of two HttpServlet classes, ServletA and ServletB, andthe ServerletA service method:  20. String key = "com.example.data";  21. session.setAttribute(key, "Hello");  22. object value = session.getAttribute(key);  23. Assume session is an HttpSession, and is not referenced anywhere else in Servlet A Which two changes, taken together, ensure that value is equal to "Hello" on line 23? (Choose two)
(A)ensure that the Servlet Bservice method is synchronized
(B)ensure that the Servlet A service method is synchronized
(C)ensure that Servlet B synchronizes on the session object when setting session attributes
(D)enclose lines 21-22 in synchronized block:synchronized(this) (session.setAttribute(key,"Hello");value = session.getAttribute(key);)
(E) enclose lines 21-22 in synchronized block:synchronized(session) (session.setAttribute(key,"Hello");value = session.getAttribute(key);)