Central concepts of Economics

Opportunity cost is decided considering heart of economy. It is sometimes very hard to reach the target skipping something which may be important also in order to get something valuable. It is really scarce after making concrete decision. It is the forgone benefit that would have been derived from an option not chosen. That is why opportunity cost is the best forgone alternative.
Example:
1.I have decided to study routinely in my free time in stead of entertainment for my good result.
2. I have chosen to take plain rice in stead of chinese food for healthy life.
3. I preferred to travel by bus in stead of CNG to save extra money