Opportunity cost can never be 0 as the second principle of Mankiw’s economics says that the cost of anything is what you give up for it.
Even if it’s money, time or another activity, there is always something that can replace the good you chose, even if it is the best one there is. As an example, if I want to buy a dress, even if I go through the entire mall and choose the best one, the opportunity cost still would not be 0, as with the time I spent searching for the dress I could have chosen a manicure or with the money I spent on the dress I could have bought the best hat.
To sum it all up, the opportunity cost can be brought to a minimum through effort and planning, but can never be quite zero.
Ilie Ioana Antonia 