For me, the right answer is D. An automated migration tool allows for complex deployments while avoiding human errors.
Ans D.

Agree with @Tony Hawk 101 below and his explanation.

B

Custom metadata is ideal for storing information that needs to be accessed by Apex classes, Visualforce pages, formula fields, and validation rules. It is recommended for list-based data. Custom metadata types are also customizable, deployable, packageable, and upgradeable. They can make ALM and compliance easier, faster, and more robust.
vs
Custom settings that is used to store configuration data and application settings, such as default values and external service endpoints. Custom settings are cached in memory, which allows for efficient access without the need for repeated database queries, hence recommended for hierarchy-based data.

Now, Considering pros & cons and also from this Exam perspective (wherein more focus is on deployment and ALM side) -
Custom Metadata Type is better option.

B - Custom Settings cannot be deployed but Custom Metadata Types can.

I would say A is correct here. The prompt says that several Apex classes depend on these custom settings, switching to a custom metadata would also require changes on all of these classes.