How to convert dual audio mkv File in to MP4

There are various ways to convert a dual audio mkv File in to MP4. You can follow following steps to Dual audio mkv to avi:
1. convert the video to xvid/avi with one of the many GUIs such as StaxRip, MeGUI
2. Extract the ac3 audio tracks using mkvtoolnix

3. mux everything together using AVI Mux GUI

You can use Divx Plus convertor which lets you to convert mkv to mk4 . After that use should use a mux software to add audio to that video.