Explanation
According to the Commerce Resources page, before installing the Cloudcraze managed package, you need to verify that customer community licenses exist, ensure that the user doing the install has a role, and create a customer community profile. Therefore, options A, D, and E are critical elements. Option B is false because the community cloud license is not required for B2B Commerce, and option C is false because you do not need a full set of Salesforce B2B Commerce data before installing the package. References: Commerce Resources, Enable Person Accounts for Commerce, Configure Internal Users for Commerce, Create a Customer Community Profile

To ensure that a store verifies shipping charges by using an external service, a developer can use two ways:
Create an Apex class implementing the sfdc_checkout.CartShippingCharges interface to retrieve shipping charges from an external service and register it as the Shipping Calculation integration in the store administration. The sfdc_checkout.CartShippingCharges interface defines the methods that a custom shipping calculation class must implement to calculate shipping charges based on the cart items, delivery groups, and shipping methods. The developer can use this interface to call an external service API and return the shipping charges for each delivery group. The developer must also register the custom Apex class as the Shipping Calculation integration in the store administration, so that it can be used by the store to verify shipping charges during checkout1.
Create an Apex class to retrieve shipping charges from an external service and update the Cart Delivery Group Methods. The Cart Delivery Group Methods object stores the shipping methods and charges for each delivery group in a cart. The developer can create an Apex class that queries this object and updates the shipping charges based on the response from an external service API. The developer can invoke this Apex class from a trigger, a process, or a flow that runs when a cart is updated or submitted2. Reference: 1: Add a Shipping Calculation Service for Commerce Stores - Salesforce Help3, 2: CartDeliveryGroupMethod Object Reference - Salesforce Help4