BCA is a 3 year degree course in Computer Application. Now if you want to take admission in it then you must be interested in it. Thus if you are asked this question then you can say-

• Computer Applications fascinates you a lot.
• You want to discover the multiple parts of the applied computer science and you want to be more practically oriented.
• You have genuine interest in Data Management/ Software Development/Coding etc and thus you think BCA will give you a scope more to work on your interest and not by theories but you will learn there application in the real world.

Now you should take this points and answer this in your own way. Also the part in which you will say you are really interested in, you should read about the basics of that portion because its very likely that you will asked a question from the area of your interest and if you can answer it then it will be great.

To know more about BCA visit the link below:

https://www.careers360.com/courses/bca-bachelor-of-computer-applications

I hope this answer helps. All the very best for your future endeavors!