The government of a small town is concerned about the litter created when people leave styrofoam cups used to serve large beverages on the ground. The government decides to tax these by implementing a $1 tax on these drinks.

D. Reduce the number of beverages sold in styrofoam cups

Explanation:

The Government is concerned about the styrofoam litter in the town and for this reason imposed a $1 on such drinks. What this will do is to make such drinks more expensive for people to buy so they will buy less of it thereby reducing the number of beverages sold in styrofoam cups.

As less of such drinks are bought, it stands to reason that less litter will accumulate as a result of styrofoam cups.