Step 1: Identifying the correct option:
Material culture refers to the tangible, physical objects that a society creates and uses - tools, buildings, clothing and technology. A mobile phone is a concrete, physical artefact, making it an example of material culture.
Step 2: Why the other options are wrong:
Language, etiquette and symbols are all intangible - they are shared meanings, norms and systems of communication, which sociologists classify as non-material (or symbolic) culture.
Final Answer:
Mobile phone (Option D)