Critical Reasoning

We have heard a good deal in recent years about the declining importance of the two major political parties. It is the mass media, we are told, that decide the outcome of elections, not the power of the parties. But it is worth noting that no independent or third-party candidate has won any important election in recent years, and in the last nationwide campaign, the two major parties raised and spent more money than ever before in support of their candidates and platforms. It seems clear that reports of the imminent demise of the two-party system are premature at best.
1. Which of the following is an assumption made in the argument above?
(A) The amount of money raised and spent by a political party is one valid criterion for judging the influence of the party.
(B) A significant increase in the number of third-party candidates would be evidence of a decline in the importance of the two major parties.
(C) The two-party system has contributed significantly to the stability of the American political structure.
(D) The mass media tend to favor an independent or third-party candidate over a candidate from one of the two major parties.
(E) The mass media are relatively unimportant in deciding the outcome of most elections.

The OA is A ..why not D ?