Press Secretary:  Our critics claim that the President’s recent highway project cancellations demonstrate a vindictive desire to punish legislative districts controlled by opposition parties.  They offer as evidence the fact that 90 percent of the projects canceled were in such districts.  But all of the canceled projects had been identified as wasteful in a report written by respected nonpartisan auditors.  So the President’s choice was clearly motivated by sound budgetary policy, not partisan politics.

Which of the following is an assumption on which the press secretary’s argument depends?

1. Canceling highway projects was not the only way for the President to punish legislative districts controlled by opposition parties.
2. The scheduled highway projects identified as wasteful in the report were not mostly projects in districts controlled by the President’s party.
3. The number of projects canceled was a significant proportion of all the highway projects that were to be undertaken by the government in the near future.
4. The highway projects canceled in districts controlled by the President’s party were not generally more expensive than the projects canceled in districts controlled by opposition parties.
5. Reports by nonpartisan auditors are not generally regarded by the opposition parties as a source of objective assessments of government projects.

为什么是B呢？