An .mkv file is a container.
It contains encoded streams of audio, video, subtitles, etc. Nothing dictates how any of those streams must be encoded. That’s up to the creator.
What matters to you is how those streams are encoded. You must find out, and you must assure that you have the proper filter installed for each of them. If you don’t have the right filter, then you can’t decode the stream so you won’t be able to see/hear/read the contents.
So, to say, 'this is an .mkv file" is to say nothing - to say, “this is a bottle” or “this is a can”. What’s important is what is IN the bottle or can, yes?
So then, this is an XVid-encoded video stream and that’s an AC3-encoded audio stream, these are the important things.
That they happen to be in an .mkv container instead of, say, an .avi container, is not so important.
I will therefore need an XVid codec and an AC3 codec if i want to view and listen to these streams. Unless I use a player with these things built in, then I must have installed them on my system separately. That is what things like the Combined Community Codec Pack - CCCP - are for.
Containers can contain multiple audio streams. These are usually for the different languages that are available. Nothing requires that one of those streams be English, and they might not be. If there are multiple audio streams, you can select the one you desire with your player. But if there is no stream for your preferred language, you’re out of luck. If there is only one audio stream, that’s the one that will be played.
Your choice has two audio streams as shown in your screenshot: one in Chinese, one in Chuukese. Only a video stream is stated to be in English, which I am going to assume are subtitles. There is no English audio stream to play.
