Please follow your passion,what you are interested in

I can't figure out if this is a serious post or you are just trolling. If this is a serious post, please provide some more information. Are you in the US? What's your visa status? What did you study in High School (if you studied in Nepal)? Did you like it? Would you like to stay in Nepal in the long term?

Study whatever the fuck you want to study, but please don't go for research field (especially Biological science, Physical science,Physics, and all those nonsense courses). You will die studying and won't be able live your life. I felt like I made a big mistake in my life so I am taking a completely different direction now. I am starting a new career with my own business ventures even after getting a PhD. I don't regret much for having wasted my time coz I have become more analytical and more capable of taking judicious decisions for myself, but life would have been much easier had I taken a different route earlier in my life.
My suggestions:
If you are really smart and hard working, study Dentistry, Medicine or even Law from good schools in the US.
If you are an average student and not so capable of taking the risks, then IT, Computer science or any engineering field is a good choice.
If you are an average, below average student, but street smart type, then study Management, finance, Political Science, International relations ( I should have gotten myself this degree and regret now for not doing this) etc.
All other degrees are worthless if you really want to see yourself as a happy individual and be able to get settled early in your life.
However, beyond all, you must do something that you would feel like you would pay someone for asking you to do what you need to feed your family. You must love your job for the rest of your life. So please be wise now than regret for the rest of your life.
Or if you are a risk taker and genuinely smart, you can simply get an undergraduate degree in management/business and start a hot-dog stall at one of the busiest streets in New York. I am damn sure you will end up being bigger than those Wall-street'ians and will achieve more than any other career professionals would achieve. 
Summary: Smart people would waste no more than 16 years of their life in school!
Good luck!

if you're in F1 visa in usa here are you choices : electrical engineering, computer science , computer engineering, all others have 80+% changes of you not finding jobs after graduation. Study what you like, follow your passon etc etc are b.s advises for average undergraduate career seeking. It was a concept introduced years ago in the US and parents are still wondering why their kids study history and anthropology in the college with loans when mr . Subrananium gets the job of engineer with 80+ k salary with the degree from Indian. first of all a 18 or 19 years have not explored the world enough to find out what their interest is let alone passion. most hormone raising kids have passion in porn, then that means they should seek a career in porn industry then? study what is good for you in the future, as you go learning you will either find a passion for it or not, but either way you'll have a good life because you can get good jobs. if you'r e in visa, forget about medicine or dentistry, you can't afford in the usa, unless your dad is bam dev etc ..if you study management or finance, trust me just having a foreign name in the field of business is a draw back, then comes accent, then the stereotyping, it's nor worth it. I have seen mbas working in gas stations. Engineering and IT is the field where you have high salary and high numbers of foreigners working. I thought physics , chemistry etc were good but i was obviously wrong from what hydrogen posted. just go for engineering dood.

@hydrogen It's surprising to know that you weren't able to find a job with a PhD degree. Loperthapa is right Most foreign ppl studying engineering or It have successful careers

@loperthapa best thing I have ever seen in Sajha

@microbiology
I was not talking about jobs, I could find thousands jobs. I was not able to get satisfaction. No matter how much you love science/research you will always find it difficult to feed your family as a postdoc.

What do you mean as a post doc? thousand jobs chahi bro leh guff deko hola didnt you apply for a faculty position? Post docs are usually for two years and you have to go to academia unless you don't have enough publications or teaching experience it sucks to hear spending so many years getting an advanced degree won't feed a family or neither a job satisfaction

yesta mull life ma euta decision lina nasakne le k garera khane hola?

Thank you Hydrogen and loperthapa.I studied Science stream in +2. I am in Nepal. Which country is easy to study undergraduate without hard struggle? How do you struggle in foreign country?

Postdocs are intellectual trap, very less paid and just another stage of exploitation. Either you should be the product of Ivy League or top 20 schools with very good publications and teaching experience, otherwise, doing Ph.D. is just a ladder to come USA after masters, absolutely non-sense. I have a very bad experience too. You will be paid half than a master's degree, my salary was decreased half after finishing Ph.D (even with engineering degree). Shame. You can't apply job for master's degree as you are overqualified. Just simple non-sense in this intellectual world.

listen kid, dont COME to US to do Undergraduate. Stay in Nepal, join a Private College ( TU PU whatever ) and study Computer Engineering or IT or Computer Science. Come to US after 4 years for Masters and you stat making big money.

Enjoy your life in Nepal, enjoy your motorbike and bang lot of bitches. Life is fun there not here working in Gas stations.

Completely agree with Hydrogen Sulfide and Loperthapa.

If you want to have a job in US, go for computer science, electrical or mechanical eng. etc.
If you have green card, go for nursing.
Never ever go for pure science such as physics, chemistry, biology etc.