Which one of the following words/phrases is most appropriately used to denote "an interoperable network of 3D virtual worlds that can be accessed simultaneously by millions of users, who can exert property rights over virtual items"?

1. A

   Big data analytics

   Big data analytics. Processing large datasets, not a 3D virtual-world network.

2. B

   Cryptography

   Cryptography. Securing information, not the world itself.

3. C

   Metaverse

   Metaverse. Interoperable 3D virtual worlds, simultaneous users, virtual property rights.

4. D

   Virtual matrix

   Virtual matrix. Not the standard term for this definition.

Summary. Official key is (c) metaverse. The stem is the usual definition: linked 3D virtual worlds, many users at once, who can hold rights in virtual items. Big data and cryptography are neighbouring tech, not that place.