Why Does Household Production Still Exist

Multiple Choice

Why does household production still exist?  

A)  because for some households the opportunity cost of production at home is greater than the cost of purchasing the good in the market 
B)  because for some households the opportunity cost of production at home is less than the cost of purchasing the good in the market 
C)  because for some households the value of home production exceeds the sunk cost of home production 
D)  because for some households the value of home production is less than the variable cost of home production