Markets can be missing for a variety of reasons:

a. lack of technology that would make the exchanges possible.
b. buyers and sellers do not know one another public policy prevents the market from existing.
c. there are too many buyers and not enough sellers.
d. lack of accurate information or communication between potential buyers and sellers

a. lack of technology that would make the exchanges possibled. lack of accurate information or communication between potential buyers and sellers

Explanation:

A missing market is one that is a competitive market and allows for the exchange of commodities but does exist in reality. A classical example is of the externalities of the pollution and can be also due to the coordinated failures that prevent the market form the formation and another barrier is the technology and failure of the information and the trust.

Can you choose anything?

Took the words right out of my fingers