What modification allows an Open Commerce API call to successfully execute when adding products to a basket?

The correct modification that allows an Open Commerce API call to successfully execute when adding products to a basket involves changing the "methods" value to include "get" and "post".

In the context of the Open Commerce API, the "methods" value specifies the types of HTTP methods that are allowed for a particular endpoint. When adding products to a basket, a POST request is essential because this method is used to send data to the server to create new resources—in this case, to add items to the shopping basket. The inclusion of "get" in the methods also allows for retrieving data about the basket, offering flexibility in the integration. Therefore, using "get" and "post" together enables both the addition of items and the ability to query basket details, making this combination necessary for a successful call.

The other options either add incorrect values or don't address the method required for modifying the basket efficiently.