How do you fix this problem?

You are debugging a problem with a shopping cart price rule which gives free shipping for the whole cart if the subtotal is greater than $100. You are seeing that when a custom shipping method is selected, the shipping price is still present even though the subtotal is greater than $100.

How do you fix this problem?
A . Create an option allow_freeshiping in the system configuration of the shipping method and set its value to 1
B. Add the shipping method’s code to the price rule action
C. Modify the carrier class to process the free_shipping flag of the quote items
D. Add the shipping method’s code to the price rule condition

Answer: A