Which course should I pursue MCA, web designing or ethical hacking?

Hi, You should go as per your interest. Either it is web designing or ethical hacking, both the fields have high demands and both have the skills that are compatible with MCA, web designing as well as ethical hacking. Both have different scopes, it depends on you whether you would go for web design

Ethical hacking is very niche specialization with limited career opportunities. Web designer requirement is very high, but it is also very competitive. You must choose your career based on interests, not on scope to excel in professional career.