Hi All
Yingtang is right, let's exam a very simple example, we will find out.
Customer buy goods, he/she can pay in cash or credit card. in this case, We may use adaptor
pattern as a solution, then we do not need a additional public method in our domain.
Payment---------more alternative Payment
/ \
/ \
CashPayment CreditCardPayment
our Domain only needs deal with Payment.
I hope It will help someone who chosen "D"