My teacher gave us a practice test and I would just like to know why the answer is (b) to the following question:

Any new class you create from an existing class is called a(n)

(a) base class (b) derived class (c) superclass (d) extended class.
I had chosen (d) but I knew it had to be between (b) and (d). I would appreciate it if someone could explain this in a bit more detail so that I can understand the answer rather than just memorize it.

Any input would be greatly appreciated!
Thanks in advance!