A binary tree traversal method that visits the root first and then recursively traverses the left and right subtrees is called

What can be used to extend an existing class so as to create a more specific class?

A. Inheritance B. Encapsulation C. Polymorphism D. Abstraction

Mobile broadband service is offered by the following wireless cellular phone service providers, EXCEPT _____.

A. Comcast B. Verizon C. AT&T D. Sprint