dTMP合成的直接前体是

A．dUMP

B．TMP

C．IDP

D．dUDP

E．dCMP

For price discrimination to work, the seller must face a market with all of the following characteristics EXCEPT:（）

A. high barriers to entry.

B. a downward sloping demand curve.

C. two or more identifiable groups of customers with different price elasticities of demand for the product.