Task: Text Completion
Input (English): [header] How to video chat on facebook [title] Open a conversation with the person you want to video chat with. [step] Make sure to open a conversation with a single person. You cannot currently start a video chat with a group. <sep> (A) You may have to wait at least a few days (at least) to open a conversation on facebook. If there is no chat app on your device, or you have to use an app like facetime or google plus then a full screen chat will be available. (B) [substeps] Use caution and make sure the person you want to chat with is available to chat with you before you start chatting. Opening a chat with only two people is very difficult. (C) You can prolong the conversation by hanging up the phone. [title] Type your contact's name in the message field in your conversation. (D) [title] Tap the video chat button at the top of the conversation. [step] This will begin calling the other person.
Output (English): D