See if I explain the difference between them in a set fashion, then Artificial Intelligence is a super set and Machine Learning and other branches are subsets of the same domain. In general Artificial Intelligence contains many things under it's hood like Machine Learning, Natural language Processing, Computer Vision and many other things.

So, the future scope of all of them are going to be crazily great as these are very hot fields nowadays and they are here to stay. So, study the syllabus and go after whatever interests you the most as the opportunities are the same in all of them.

Hope I have answered your question. All the best!