To avoid having to use fully qualified referenced classes, you could:
a. Add a reference to the class.
b. Add an import statement for the class.
c. Add a using directive.
d. Inherit from the class.
e. Package the classes in the same solution.
The correct answer is b. Add an import statement for the class.
If a class is imported in the namespace then the Fully-qualified class names are always valid. OrganizationNamespace added to avoid fully qualifying references.