I think road is the building block of any country. A lot of people say it's education, but goods and services and business cannot arrive without road. And educated people(e.g. doctors) usually don't want to go to a place where there is no goods and services. I don't think electricity is the biggest source of income for Nepal. Becuase it's too expensive to produce. Who is going to invest on it? Then we again have to rely on foreign countries.... The only thing that nepal is rich, is on it's natural beauty, which requires minimal investment and maximum profit. So tourism is best souce of income for nepal.