Call market characteristics

Which is least likely characteristic of a call market? A.primary market B.secondary market with participation by a small number of active investors-traders in which buy-sell orders are cleared at a single equilibrium price I thought both A and D are not its characteristics…any help? Thx.

I think the answer is A. “A type of market in which each transaction takes place at predetermined intervals and where all of the bid and ask orders are aggregated and transacted at once. The exchange determines the market clearing price based on the number of bid and ask orders. A call market is contrasted to an auction market, where orders are filled as soon as a buyer/seller is found for any given order at an agreed upon price. In a call market, the price is set by the exchange so the market will clear, or almost clear, every time orders are filled. This is in stark contrast to the auction market, where prices are determined by buyers and sellers. Because the call market groups transactions together, there is a substantial increase in liquidity. Although liquidity is generally considered to be a good quality in any marketplace, sellers may lose some of the liquidity premium, which is can be substantial.” Quoted from