A working model is known as:

✅ Explanation: A mock-up is a working model of a product or system, used for testing, demonstration, design evaluation, or other purposes. It is a prototype that is not fully functional but allows for interaction and testing of certain features.

📌 Other Options Explanations:
(a) Objects: An object is a material thing that can be seen and touched.
(b) Model: A model is a three-dimensional representation of a person or thing or of a proposed structure, typically on a smaller scale than the original.  
(d) Poster: A poster is a large printed picture used for decoration or advertisement.