Which two actions will achieve this goal?

You are developing a web application that consumes services from a third-party application. A web worker
processes the third-party application requests in the background. A page in the application instantiates the web
worker process.
You need to establish two-way communications between the web worker process and the page.
Which two actions will achieve this goal? (Each correct answer presents a complete solution. Choose two.)

A.
From the web worker, use the onopen event handler of the main page to capture events.

B.
From the main page, use the onmessage event handler of the web worker to capture events.

C.
From the web worker, use the onmessage event handler of the main page to capture events.

D.
From the main page, use the onopen event handler of the web worker to capture events.

Explanation:
* When postMessage() is called from the main page, our worker handles that message by defining an
onmessage handler for the message event.
* Server-Sent Events – One Way Messaging
A server-sent event is when a web page automatically gets updates from a server.
Receive Server-Sent Event Notifications
The EventSource object is used to receive server-sent event notifications:
Example
var source = new EventSource(“demo_sse.php”);
source.onmessage = function(event) {
document.getElementById(“result”).innerHTML += event.data + “<br>”;
};

http://www.w3schools.com/html/html5_serversentevents.asp
http://www.html5rocks.com/en/tutorials/workers/basics/