The quantity of newspapers sold will decline if a. magazine prices rise. b. prices are reduced. c. the printers' union makes wage concessions. d. newsprint becomes more expensive.

The quantity of newspapers sold will decline if

d. newsprint becomes more expensive.

Explanation:

The reason for this is the demand curve. The demand curve is the relationship between the price of newspaper and the quantity demanded. As price rises, people would have less capacity and willingness to buy newspaper therefore reducing the quantity sold.

Why not other options:

a. magazine prices rise - magazine is a substitute of newspaper and if price of magazine rises then people will start buying more newspaper and therefore increasing the sales of newspaper instead of declining.

b. prices are reduced - If the prices are reduced, more and more people will have capacity to buy newspaper thus increasing sales instead of reduction.

c. the printers' union makes wage concessions - If cost of manufacturing newspaper is decreased (union takes low salaries now), selling price will also be lowered. This will result in increase of sales of newspaper rather than reduction