Step 1: Meaning of GI Tag.
The term GI stands for \textit{Geographical Indication}.
It is used to identify goods, products, or crafts which originate from a specific geographical region.
The GI tag ensures that the product has certain qualities, reputation, or characteristics directly linked to that origin.
Step 2: Legal Framework.
In India, GI tags are governed under the \textit{Geographical Indications of Goods (Registration and Protection) Act, 1999}.
This Act came into force in 2003 and provides legal protection to products registered under GI.
For example, Darjeeling Tea was the first Indian product to get a GI tag.
Step 3: Analysis of the options.
(A) Geographical Index: Incorrect, because “Index” refers to a listing or measurement and not to certification of origin.
(B) Geography Index: Incorrect, since this is not a recognized terminology in international or Indian law.
(C) Geographical Indicator: Correct, because it is the globally accepted full form of GI tag.
(D) Geography Indicator: Incorrect, as “Geography Indicator” is not a legal or standard term.
Step 4: Conclusion.
Therefore, the correct full form of GI tag is Geographical Indicator, which gives recognition and protection to products linked with their place of origin.