Let's match the items:
A. HMT (Hindustan Machine Tools): This is a well-known Public sector company in India. So, A matches with II.
B. Milk union: Milk unions, like Amul, are classic examples of a Co-operative society. So, B matches with IV.
C. Fixed capital: Fixed capital refers to assets and capital investments that are not consumed or destroyed in the production of a good, such as a Building. So, C matches with I.
D. Regional market: A regional market's scope is defined by a geographical area, such as a Town or a group of towns. So, D matches with III.
The correct matching is A-II, B-IV, C-I, D-III.